Network+ Certification Readiness Review (Pro-Certification)

PUBLISHED BY Microsoft Press A Division of Microsoft Corporation One Microsoft Way Redmond, Washington 98052-6399 Copyr...

Author: Craig Zacker

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PUBLISHED BY Microsoft Press A Division of Microsoft Corporation One Microsoft Way Redmond, Washington 98052-6399 Copyright © 2002 by Microsoft Corporation All rights reserved. No part of the contents of this book may be reproduced or transmitted in any form or by any means without the written permission of the publisher. Library of Congress Cataloging-in-Publication Data Zacker, Craig. Network+ Certification Readiness Review / Craig Zacker. p. cm. Includes index. ISBN 0-7356-1457-1 1. Electronic data processing personnel--Certification. 2. Computer networks--Examinations--Study guides. I. Title: Network plus certification readiness review. II. Title QA76.3 .Z33 004.6

2001 2001051187

Printed and bound in the United States of America. 1 2 3 4 5 6 7 8 9

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Distributed in Canada by Penguin Books Canada Limited. A CIP catalogue record for this book is available from the British Library. Microsoft Press books are available through booksellers and distributors worldwide. For further information about international editions, contact your local Microsoft Corporation office or contact Microsoft Press International directly at fax (425) 936-7329. Visit our Web site at www.microsoft.com/mspress. Send comments to [email protected]. Active Directory, Microsoft, Microsoft Press, MS-DOS, Windows, and Windows NT are either registered trademarks or trademarks of Microsoft Corporation in the United States and/or other countries. Other product and company names mentioned herein may be the trademarks of their respective owners. The example companies, organizations, products, domain names, e-mail addresses, logos, people, places, and events depicted herein are fictitious. No association with any real company, organization, product, domain name, e-mail address, logo, person, place, or event is intended or should be inferred. Microsoft Press Acquisitions Editor: Thomas Pohlmann Project Editor: Kurt Stephan

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nSight, Inc. Project Manager: Lisa A. Wehrle Technical Editor: Robert Hogan Manuscript Editor: Stephanie English Desktop Publisher: Patty Fagan Indexer: Jack Lewis

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Contents Welcome to Network+ Certification ............................................................................. ix Before You Begin.................................................................................................... ix Using the Network+ Readiness Review.................................................................. xi Exam Objectives Summary.................................................................................. xvii Getting More Help ..................................................................................................xx

Objective Domain 1: Media and Topologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Tested Skills and Suggested Practices.......................................................................1 Further Reading.........................................................................................................3 Objective 1.1: Recognize the following logical or physical network topologies given a schematic diagram or description: star/hierarchical, bus, mesh, ring, wireless. ..........5 Questions...................................................................................................................7 Answers.....................................................................................................................8 Objective 1.2: Specify the main features of 802.2 (LLC), 802.3 (Ethernet), 802.5 (token ring), 802.11b (wireless), and FDDI networking technologies, including speed, access method, topology, media.........................................................................11 Questions.................................................................................................................14 Answers...................................................................................................................15 Objective 1.3: Specify the characteristics (e.g., speed, length, topology, cable type, etc.) of the following: 802.3 (Ethernet) standards, 10BASE-T, 100BASE-TX, 10BASE2, 10BASE5, 100BASE-FX, Gigabit Ethernet. ..............................................17 Questions.................................................................................................................20 Answers...................................................................................................................21 Objective 1.4: Recognize the following media connectors and/or describe their uses: RJ-11, RJ-45, AUI, BNC, ST, SC. .......................................................................25 Questions.................................................................................................................27 Answers...................................................................................................................28 Objective 1.5: Choose the appropriate media type and connectors to add a client to an existing network. ..................................................................................................31 Questions.................................................................................................................33 Answers...................................................................................................................34 Objective 1.6: Identify the purpose, features, and functions of the following network components: hubs, switches, bridges, routers, gateways, CSU/DSUs, network interface cards/ISDN adapters/system area network cards, wireless access points, modems. ..........................................................................................................35 Questions.................................................................................................................38 Answers...................................................................................................................39

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Readiness Review—Exam N10-002

Objective Domain 2: Protocols and Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Tested Skills and Suggested Practices .................................................................... 43 Further Reading ...................................................................................................... 47 Objective 2.1: Given an example, identify a MAC address.......................................... 53 Questions ................................................................................................................ 54 Answers .................................................................................................................. 55 Objective 2.2: Identify the seven layers of the OSI model and their functions. ........... 57 Questions ................................................................................................................ 60 Answers .................................................................................................................. 61 Objective 2.3: Differentiate between the following network protocols in terms of routing, addressing schemes, interoperability, and naming conventions: TCP/IP, IPX/SPX, NetBEUI, AppleTalk. .................................................................................. 63 Questions ................................................................................................................ 66 Answers .................................................................................................................. 67 Objective 2.4: Identify the OSI layers at which the following network components operate: hubs, switches, bridges, routers, network interface cards............................... 69 Questions ................................................................................................................ 71 Answers .................................................................................................................. 72 Objective 2.5: Define the purpose, function and/or use of the following protocols within TCP/IP: IP, TCP, UDP, FTP, TFTP, SMTP, HTTP, HTTPS, POP3/IMAP4, TELNET, ICMP, ARP, NTP.......................................................................................... 73 Questions ................................................................................................................ 76 Answers .................................................................................................................. 77 Objective 2.6: Define the function of TCP/UDP ports. Identify well-known ports. ............................................................................................................................. 81 Questions ................................................................................................................ 83 Answers .................................................................................................................. 84 Objective 2.7: Identify the purpose of the following network services (e.g., DHCP/ BOOTP, DNS, NAT/ICS, WINS, and SNMP).............................................................. 87 Questions ................................................................................................................ 90 Answers .................................................................................................................. 91 Objective 2.8: Identify IP addresses (IPv4, IPv6) and their default subnet masks....... 93 Questions ................................................................................................................ 95 Answers .................................................................................................................. 96 Objective 2.9: Identify the purpose of subnetting and default gateways. ..................... 99 Questions .............................................................................................................. 101 Answers ................................................................................................................ 102

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Objective 2.10: Identify the differences between public vs. private networks............103 Questions...............................................................................................................105 Answers.................................................................................................................106 Objective 2.11: Identify the basic characteristics (e.g., speed, capacity, media) of the following WAN technologies: packet switching vs. circuit switching, ISDN, FDDI, ATM, Frame Relay, SONET/SDH, T1/E1, T3/E3, OCx. ................................107 Questions...............................................................................................................110 Answers.................................................................................................................111 Objective 2.12: Define the function of the following remote access protocols and services: RAS, PPP, PPTP, ICA. ..........................................................................113 Questions...............................................................................................................115 Answers.................................................................................................................116 Objective 2.13: Identify the following security protocols and describe their purpose and function: IPsec, L2TP, SSL, Kerberos..................................................................117 Questions...............................................................................................................119 Answers................................................................................................................ 120

Objective Domain 3: Network Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 Tested Skills and Suggested Practices...................................................................121 Further Reading.....................................................................................................124 Objective 3.1: Identify the basic capabilities (i.e., client support, interoperability, authentication, file and print services, application support, and security) of the following server operating systems: UNIX/Linux, NetWare, Windows, Macintosh....................................................................................................................127 Questions...............................................................................................................129 Answers.................................................................................................................130 Objective 3.2: Identify the basic capabilities (i.e., client connectivity, local security mechanisms, and authentication) of the following clients: NetWare, UNIX/Linux, Windows, Macintosh...................................................................................................133 Questions...............................................................................................................135 Answers.................................................................................................................136 Objective 3.3: Identify the main characteristics of VLANs........................................137 Questions...............................................................................................................138 Answers.................................................................................................................139 Objective 3.4: Identify the main characteristics of network attached storage. ...........141 Questions...............................................................................................................143 Answers.................................................................................................................145

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Readiness Review—Exam N10-002 Objective 3.5: Identify the purpose and characteristics of fault tolerance.................. 147 Questions .............................................................................................................. 149 Answers ................................................................................................................ 150 Objective 3.6: Identify the purpose and characteristics of disaster recovery.............. 153 Questions .............................................................................................................. 155 Answers ................................................................................................................ 156 Objective 3.7: Given a remote connectivity scenario (e.g., IP, IPX, dial-up, PPPoE, authentication, physical connectivity, etc.), configure the connection. ...................... 159 Questions .............................................................................................................. 161 Answers ................................................................................................................ 162 Objective 3.8: Identify the purpose, benefits, and characteristics of using a firewall. ....................................................................................................................... 165 Questions .............................................................................................................. 167 Answers ................................................................................................................ 168 Objective 3.9: Identify the purpose, benefits, and characteristics of using a proxy. ....................................................................................................................... 171 Questions .............................................................................................................. 173 Answers ................................................................................................................ 174 Objective 3.10: Given a scenario, predict the impact of a particular security implementation on network functionality (e.g., blocking port numbers, encryption, etc.). ......................................................................................................... 177 Questions .............................................................................................................. 179 Answers ................................................................................................................ 179 Objective 3.11: Given a network configuration, select the appropriate NIC and network configuration settings (DHCP, DNS, WINS, protocols, NetBIOS/host name, etc.)................................................................................................................... 181 Questions .............................................................................................................. 184 Answers ................................................................................................................ 185

Objective Domain 4: Network Support. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 Tested Skills and Suggested Practices .................................................................. 187 Further Reading .................................................................................................... 190 Objective 4.1: Given a troubleshooting scenario, select the appropriate TCP/IP utility from among the following: Tracert, Ping, Arp, Netstat, Nbtstat, Ipconfig/Ifconfig, Winipcfg, Nslookup. ..................................................................... 193 Questions .............................................................................................................. 196 Answers ................................................................................................................ 197

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Objective 4.2: Given a troubleshooting scenario involving a small office/home office network failure (e.g., xDSL, cable, home satellite, wireless, POTS), identify the cause of the failure. ...............................................................................................201 Questions...............................................................................................................204 Answers.................................................................................................................205 Objective 4.3: Given a troubleshooting scenario involving a remote connectivity problem (e.g., authentication failure, protocol configuration, physical connectivity), identify the cause of the problem. ........................................................207 Questions...............................................................................................................210 Answers.................................................................................................................211 Objective 4.4: Given specific parameters, configure a client to connect to the following servers: UNIX/Linux, NetWare, Windows, Macintosh. .............................213 Questions...............................................................................................................215 Answers.................................................................................................................216 Objective 4.5: Given a wiring task, select the appropriate tool (e.g., wire crimper, media tester/certifier, punch down tool, tone generator, optical tester, etc.)...............219 Questions...............................................................................................................222 Answers.................................................................................................................223 Objective 4.6: Given a network scenario, interpret visual indicators (e.g., link lights, collision lights, etc.) to determine the nature of the problem...........................225 Questions...............................................................................................................227 Answers.................................................................................................................228 Objective 4.7: Given output from a diagnostic utility (e.g., Tracert, Ping, Ipconfig, etc.), identify the utility and interpret the output. .......................................................231 Questions...............................................................................................................234 Answers.................................................................................................................235 Objective 4.8: Given a scenario, predict the impact of modifying, adding, or removing network services (e.g., DHCP, DNS, WINS, etc.) on network resources and users......................................................................................................................237 Questions...............................................................................................................239 Answers.................................................................................................................240 Objective 4.9: Given a network problem scenario, select an appropriate course of action based on a general troubleshooting strategy. ...............................................243 Questions...............................................................................................................245 Answers.................................................................................................................246

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Readiness Review—Exam N10-002 Objective 4.10: Given a troubleshooting scenario involving a network with a particular physical topology (i.e., bus, star/hierarchical, mesh, ring, and wireless) and including a network diagram, identify the network area affected and the cause of the problem............................................................................................................. 249 Questions ............................................................................................................. 251 Answers ................................................................................................................ 254 Objective 4.11: Given a network troubleshooting scenario involving a client connectivity problem (e.g., incorrect protocol/client software/authentication configuration, or insufficient rights/permission), identify the cause of the problem. ...................................................................................................................... 257 Questions ............................................................................................................. 259 Answers ................................................................................................................ 260 Objective 4.12: Given a network troubleshooting scenario involving a wiring/ infrastructure problem, identify the cause of the problem (e.g., bad media, interference, network hardware). ................................................................................ 263 Questions .............................................................................................................. 265 Answers ................................................................................................................ 267 Glossary ..................................................................................................................... 269 Index........................................................................................................................... 289

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Welcome to Network+ Certification

Welcome to Network+ Certification Readiness Review. The Readiness Review series gives you a focused, timesaving way to identify the information you need to know to pass the Computing Technology Industry Association (CompTIA) Network+ Certification exam. The series combines a realistic electronic assessment with a review book to help you become familiar with the types of questions that you will encounter on the Network+ exam. By reviewing the objectives and sample questions, you can focus on the specific skills that you need to improve before taking the exam. This book helps you evaluate your readiness for the CompTIA exam N10-002. When you pass this exam, you earn the CompTIA Network+ Certification. You can find a complete list of CompTIA exams and their related objectives on the CompTIA Web site at http://www.comptia.com. The Readiness Review series lets you identify any areas in which you might need additional training.To help you get the training you need to successfully pass the certification exams, Microsoft Press publishes a complete line of self-paced training kits and other study materials. For comprehensive information about the topics covered in the Network+ exam, see the corresponding training kit—Network+ Certification Training Kit.

Before You Begin This Readiness Review consists of two main parts: the Readiness Review electronic assessment program on the accompanying compact disc and this Readiness Review book.

The Readiness Review Components The electronic assessment is a practice certification test that helps you evaluate your skills. It provides instant scoring feedback, so you can determine areas in which additional study might be helpful before you take the certification exam. Although your score on the electronic assessment does not necessarily indicate what your score will be on the certification exam, it does give you the opportunity to answer questions that are similar to those on the actual certification exam.

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Readiness Review—Exam N10-002 The Readiness Review book is organized by the exam’s objectives. Each chapter of the book pertains to one of the four primary groups of objectives on the actual exam, called the Objective Domains. Each Objective Domain lists the skills you need to master to answer the exam questions. Because the certification exams focus on real-world skills, the Tested Skills and Suggested Practices lists provide practices that emphasize the practical application of the exam objectives. Each Objective Domain also provides suggestions for further reading or additional resources to help you understand the objectives and increase your ability to perform the task or skills specified by the objectives. Within each Objective Domain, you will find the related objectives that are covered on the exam. Each objective provides you with the following:

Key terms you must know to understand the objective. Knowing these terms can help you answer the objective’s questions correctly. Several sample exam questions with the correct answers. The answers are accompanied by explanations of each correct and incorrect answer. (These questions match the questions on the electronic assessment.) You use the electronic assessment to determine the exam objectives that you need to study, and then use the Readiness Review book to learn more about those particular objectives and discover additional study materials to supplement your knowledge. You can also use the Readiness Review book to research the answers to specific sample test questions. Keep in mind that to pass the exam, you should understand not only the answer to the question, but also the concepts on which the correct answer is based.

Network+ Certification Exam Prerequisites No exams or classes are required before you take the Network+ exam. However, in addition to the skills tested by the exam, you should have a working knowledge of the operation and support of hardware and software on a personal computer. After you have used the Readiness Review and determined that you are ready for the exam, use the Get Exam Information link provided on the home page of the electronic assessment tool for information on scheduling for the exam. You can schedule exams up to six weeks in advance or as late as one working day before the exam date.

Know the Products CompTIA’s certification program relies on exams that measure your ability to perform a specific job function or set of tasks. CompTIA develops the exams by analyzing the tasks performed by people who are currently working in the field. Therefore, the specific knowledge, skills, and abilities relating to the job are reflected in the certification exam.


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Because the certification exams are based on real-world tasks, you need to gain handson experience with the applicable technology in order to master the exam. In a sense, you might consider hands-on experience in an organizational environment to be a prerequisite for passing the Network+ exam. Many of the questions relate directly to specific network products or technologies, so use opportunities at your school or workplace to practice using the relevant tools.

Using the Network+ Readiness Review Although you can use the Readiness Review in a number of ways, you might start your studies by taking the electronic assessment as a pretest. After completing the exam, review your results for each Objective Domain and focus your studies first on the Objective Domains for which you received the lowest scores. The electronic assessment allows you to print your results, and a printed report of how you fared can be useful when reviewing the exam material in this book. After you have taken the Readiness Review electronic assessment, use the Readiness Review book to learn more about the Objective Domains that you find difficult and to find listings of appropriate study materials that might supplement your knowledge. By reviewing why the answers are correct or incorrect, you can determine if you need to study the objective topics more. You can also use the Readiness Review book to focus on the exact objectives that you need to master. Each objective in the book contains several questions that help you determine if you understand the information related to that particular skill. The book is also designed for you to answer each question before turning the page to review the correct answer. The best method to prepare for the Network+ exam is to use the Readiness Review book in conjunction with the electronic assessment and other study material. Thoroughly studying and practicing the material combined with substantial real-world experience can help you fully prepare for the Network+ exam.

Understanding the Readiness Review Conventions Before you start using the Readiness Review, it is important that you understand the terms and conventions used in the electronic assessment and book.

Question Numbering System The Readiness Review electronic assessment and book contain reference numbers for each question. Understanding the numbering format will help you use the Readiness Review more effectively. When CompTIA creates the exams, the questions are grouped by job skills called objectives. These objectives are then organized by sections known

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Readiness Review—Exam N10-002 as Objective Domains. Each question can be identified by the Objective Domain and the objective it covers. The question numbers follow this format: Test Number.Objective Domain.Objective.Question Number For example, question number N10-002.02.01.003 means this is question three (003) for the first objective (01) in the second Objective Domain (02) of the Network+ exam (N10-002). Refer to the “Exam Objectives Summary” section later in this introduction to locate the numbers associated with particular objectives. Each question is numbered based on its presentation in the printed book. You can use this numbering system to reference questions on the electronic assessment or in the Readiness Review book. Even though the questions in the book are organized by objective, questions in the electronic assessment and actual certification exam are presented in random order.

Notational Conventions Characters or commands that you type appear in bold lowercase type. Variable information and URLs are italicized. Italic is also used for book titles. Acronyms and filenames appear in FULL CAPITALS.

Notes Notes appear throughout the book.

Notes marked Caution contain information you will want to know before continuing with the book’s material. Notes marked Note contain supplemental information. Notes marked Tip contain helpful process hints.

Using the Readiness Review Electronic Assessment The Readiness Review electronic assessment simulates the actual Network+ exam. Each iteration of the electronic assessment consists of 50 questions covering all the objectives for the Network+ exam. (The actual Network+ Certification exam consists of 65 questions.) Just like a real certification exam, you see questions from the objectives in random order during the practice test. Similar to the certification exam, the electronic assessment allows you to mark questions and review them after you finish the test. To increase its value as a study aid, you can take the electronic assessment multiple times. Each time you are presented with a different set of questions in a revised order; however, some questions may be repeated.


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If you have used one of the certification exam preparation tests available from Microsoft, the Readiness Review electronic assessment should look familiar. The difference is that this electronic assessment gives you the opportunity to learn as you take the exam.

Installing and Running the Electronic Assessment Software Before you begin using the electronic assessment, you need to install the software. You need a computer with the following minimum configuration:

Multimedia PC with a 75 MHz Pentium or higher processor 16 MB RAM for Windows 95 or Windows 98, or 32 MB RAM for Windows Me or Windows NT, or 64 MB RAM for Windows 2000 or Windows XP Internet Explorer 5.01 or later 17 MB of available hard disk space (additional 13 MB minimum of hard disk space to install Internet Explorer 6.0 from this CD-ROM) A double-speed CD-ROM drive or better Super VGA display with at least 256 colors

To install the electronic assessment 1. Insert the Readiness Review companion CD-ROM into your CD-ROM drive. A starting menu will display automatically, with links to the resources included on the CD-ROM. Note If your system does not have Microsoft Internet Explorer 5.01 or later, you can install Internet Explorer 6.0 now by selecting the appropriate option on the menu. 2. Click Install Readiness Review. A dialog box appears, indicating that you will install the Readiness Review to your computer. 3. Click Next. The License Agreement dialog box appears. 4. To continue with the installation of the electronic assessment engine, you must accept the License Agreement by clickingYes.

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Readiness Review—Exam N10-002 5. The Choose Destination Location dialog box appears showing a default installation directory. Either accept the default or change the installation directory if needed. Click Next to copy the files to your hard disk. 6. A Question dialog box appears asking whether you would like Setup to create a desktop shortcut for this program. If you click Yes, an icon will be placed on your desktop. 7. The Setup Complete dialog box appears. Select whether you want to view the README.TXT file after closing the Setup program, and then click Finish. The electronic assessment software is completely installed. If you chose to view the README.TXT file, it will launch in a new window. For optimal viewing, enable word wrap.

To start the electronic assessment 1. From the Start menu, point to Programs, point to MCSE Readiness Review, then click RR Exam N10-002. The electronic assessment program starts. 2. Click Start Test. Information about the electronic assessment program appears. 3. Click OK.

Taking the Electronic Assessment The Readiness Review electronic assessment consists of 50 multiple-choice questions, and as in the certification exam, you can skip questions or mark them for later review. Each exam question contains a question number that you can use to refer back to the Readiness Review book. Before you end the electronic assessment, you should be sure to answer all the questions. When the exam is graded, unanswered questions are counted as incorrect and will lower your score. Similarly, on the actual certification exam you should complete all questions or they will be counted as incorrect. No trick questions appear on the exam. The correct answer will always be among the list of choices. Some questions may have more than one correct answer, and this will be indicated in the question. A good strategy is to eliminate the most obvious incorrect answers first to make it easier for you to select the correct answer. You have 70 minutes to complete the electronic assessment. During the exam you will see a timer indicating the amount of time you have remaining. This will help you to gauge the amount of time you should use to answer each question and to complete the exam.


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Ending and Grading the Electronic Assessment When you click Score Test, you have the opportunity to review the questions you marked or left incomplete. (This format is not similar to the one used on the actual certification exam, in which you can verify whether you are satisfied with your answers and then click Grade Test.) The electronic assessment is graded when you click Score Test, and the software presents your section scores and your total score. You can always end a test without grading your electronic assessment by clicking Home. After your electronic assessment is graded, you can view the correct and incorrect answers by clicking Review Questions.

Interpreting the Electronic Assessment Results The Score screen shows you the number of questions in each Objective Domain section, the number of questions you answered correctly, and a percentage grade for each section. You can use the Score screen to determine where to spend additional time studying. On the actual certification exam, the number of questions and passing score will depend on the exam you are taking. The electronic assessment records your score each time you grade an exam so that you can track your progress over time.

To view your progress and exam records 1. From the electronic assessment Main menu, click View History. Each test attempt score appears. 2. Click on a test attempt date/time to view your score for each Objective Domain. Review these scores to determine which Objective Domains you should study further. You can also use the scores to determine your progress.

Using the Readiness Review Book You can use the Readiness Review book as a supplement to the Readiness Review electronic assessment, or as a stand-alone study aid. If you decide to use the book as a stand-alone study aid, review the Table of Contents or the list of objectives to find topics of interest or an appropriate starting point for you. To get the greatest benefit from the book, use the electronic assessment as a pretest to determine the Objective Domains for which you should spend the most study time. Or, if you would like to research specific questions while taking the electronic assessment, you can use the question number located on the question screen to reference the question number in the Readiness Review book.

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Readiness Review—Exam N10-002 One way to determine areas in which additional study may be helpful is to carefully review your individual section scores from the electronic assessment and note objective areas where your score could be improved. The section scores correlate to the Objective Domains listed in the Readiness Review book.

Reviewing the Objectives Each Objective Domain in the book contains an introduction and a list of practice skills. Each list of practice skills describes suggested tasks you can perform to help you understand the objectives. Some of the tasks suggest reading additional material, while others are hands-on practices with software or hardware.You should pay particular attention to the hands-on practices, as the certification exam reflects real-world knowledge you can gain only by working with the software or technology. Increasing your real-world experience with the relevant products and technologies will improve your performance on the exam. Once you have chosen the objectives you would like to study, turn to the Table of Contents to locate the objectives in the Readiness Review book. You can study each objective separately, but you may need to understand the concepts explained in other objectives. Make sure you understand the key terms for each objective—you will need a thorough understanding of these terms to answer the objective’s questions correctly. Key term definitions are located in the Glossary of this book.

Reviewing the Questions Each objective includes questions followed by the possible answers. After you review the question and select a probable answer, turn to the Answers section to determine if you answered the question correctly. (For information about the question numbering format, see “Question Numbering System,” earlier in this introduction.) The Readiness Review briefly discusses each possible answer and explains why each answer is correct or incorrect. After reviewing each explanation, if you feel you need more information about a topic, question, or answer, refer to the Further Readings section for that domain for more information. The answers to the questions in the Readiness Review are based on current industry specifications and standards. However, the information provided by the answers is subject to change as technology improves and changes.


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Exam Objectives Summary The CompTIA Network+ Certification (N10-002) exam measures your ability to configure and operate a variety of networking products. This exam covers a wide range of vendor and product neutral networking technologies that can also serve as a prerequisite for vendor-specific IT certifications. Before taking the exam, you should be proficient with the skills presented in the following sections. The sections provide the exam objectives and the corresponding objective numbers (which you can use to reference the questions in the Readiness Review electronic assessment and book) grouped by Objective Domains.

Objective Domain 1: Media and Topologies The objectives in Objective Domain 1 are as follows:

Objective 1.1 (N10-002.01.01)—Recognize the following logical or physical network topologies given a schematic diagram or description: star/hierarchical, bus, mesh, ring, wireless. Objective 1.2 (N10-002.01.02)—Specify the main features of 802.2 (LLC), 802.3 (Ethernet), 802.5 (Token Ring), 802.11b (wireless), and FDDI networking technologies, including speed, access method, topology, and media. Objective 1.3 (N10-002.01.03)—Specify the characteristics (e.g., speed, length, topology, cable type, etc.) of the following 802.3 (Ethernet) standards, 10BASE-T, 100BASE-TX, 10BASE2, 10BASE5, 100BASE-FX, Gigabit Ethernet. Objective 1.4 (N10-002.01.04)—Recognize the following media connectors and/or describe their uses: RJ-11, RJ-45, AUI, BNC, ST, SC. Objective 1.5 (N10-002.01.05)—Choose the appropriate media type and connectors to add a client to an existing network. Objective 1.6 (N10-002.01.06)—Identify the purpose, features, and functions of the following network components: hubs, switches, bridges, routers, gateways, CSU/ DSUs, network interface cards/ISDN adapters/system area network cards, wireless access points, modems.

Objective Domain 2: Protocols and Standards The objectives in Objective Domain 2 are as follows:

Objective 2.1 (N10-002.02.01)—Given an example, identify a MAC address. Objective 2.2 (N10-002.02.02)—Identify the seven layers of the OSI model and their functions.

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Objective 2.3 (N10-002.02.03)—Differentiate between the following network protocols in terms of routing, addressing schemes, interoperability, and naming conventions: TCP/IP, IPX/SPX, NetBEUI, AppleTalk. Objective 2.4 (N10-002.02.04)—Identify the OSI layers at which the following network components operate: hubs, switches, bridges, routers, network interface cards. Objective 2.5 (N10-002.02.05)—Define the purpose, function, and/or use of the following protocols within TCP/IP: IP, TCP, UDP, FTP, TFTP, SMTP, HTTP, HTTPS, POP3/IMAP4, TELNET, ICMP, ARP, NTP. Objective 2.6 (N10-002.02.06)—Define the function of TCP/UDP ports. Identify well-known ports. Objective 2.7 (N10-002.02.07)—Identify the purpose of the following network services (e.g., DHCP/BOOTP, DNS, NAT/ICS, WINS, and SNMP). Objective 2.8 (N10-002.02.08)—Identify IP addresses (IPv4, IPv6) and their default subnet masks. Objective 2.9 (N10-002.02.09)—Identify the purpose of subnetting and default gateways. Objective 2.10 (N10-002.02.10)—Identify the differences between public vs. private networks. Objective 2.11 (N10-002.02.11)—Identify the basic characteristics (e.g., speed, capacity, media) of the following WAN technologies: packet switching vs. circuit switching, ISDN, FDDI, ATM, Frame Relay, SONET/SDH, T1/E1, T3/E3, OCx. Objective 2.12 (N10-002.02.12)—Define the function of the following remote access protocols and services: RAS, PPP, PPTP, ICA. Objective 2.13 (N10-002.02.13)—Identify the following security protocols and describe their purpose and function: IPSec, L2TP, SSL, Kerberos.

Objective Domain 3: Network Implementation The objectives in Objective Domain 3 are as follows:

Objective 3.1 (N10-002.03.01)—Identify the basic capabilities (i.e., client support, interoperability, authentication, file and print services, application support, and security) of the following server operating systems: UNIX/Linux, NetWare, Windows, Macintosh. Objective 3.2 (N10-002.03.02)—Identify the basic capabilities (i.e., client connectivity, local security mechanisms, and authentication) of the following clients: NetWare, UNIX/Linux, Windows, Macintosh.


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Objective 3.3 (N10-002.03.03)—Identify the main characteristics of VLANs. Objective 3.4 (N10-002.03.04)—Identify the main characteristics of network attached storage. Objective 3.5 (N10-002.03.05)—Identify the purpose and characteristics of fault tolerance. Objective 3.6 (N10-002.03.06)—Identify the purpose and characteristics of disaster recovery. Objective 3.7 (N10-002.03.07)—Given a remote connectivity scenario (e.g., IP, IPX, dial-up, PPPoE, authentication, physical connectivity, etc.), configure the connection. Objective 3.8 (N10-002.03.08)—Identify the purpose, benefits, and characteristics of using a firewall. Objective 3.9 (N10-002.03.09)—Identify the purpose, benefits, and characteristics of using a proxy. Objective 3.10 (N10-002.03.10)—Given a scenario, predict the impact of a particular security implementation on network functionality (e.g., blocking port numbers, encryption, etc.). Objective 3.11 (N10-002.03.11)—Given a network configuration, select the appropriate NIC and network configuration settings (DHCP, DNS, WINS, protocols, NetBIOS/host name, etc.).

Objective Domain 4: Network Support The objectives in Objective Domain 4 are as follows:

Objective 4.1 (N10-002.04.01)—Given a troubleshooting scenario, select the appropriate TCP/IP utility from among the following: Tracert, Ping, Arp, Netstat, Nbtstat, Ipconfig/Ifconfig, Winipcfg, Nslookup. Objective 4.2 (N10-002.04.02)—Given a troubleshooting scenario involving a small office/home office network failure (e.g., xDSL, cable, home satellite, wireless, POTS), identify the cause of the failure. Objective 4.3 (N10-002.04.03)—Given a troubleshooting scenario involving a remote connectivity problem (e.g., authentication failure, protocol configuration, physical connectivity), identify the cause of the problem. Objective 4.4 (N10-002.04.04)—Given specific parameters, configure a client to connect to the following servers: UNIX/Linux, NetWare, Windows, Macintosh.

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Objective 4.5 (N10-002.04.05)—Given a wiring task, select the appropriate tool (e.g., wire crimper, media tester/certifier, punch down tool, tone generator, optical tester, etc.). Objective 4.6 (N10-002.04.06)—Given a network scenario, interpret visual indicators (e.g., link lights, collision lights, etc.) to determine the nature of the problem. Objective 4.7 (N10-002.04.07)—Given output from a diagnostic utility (e.g., Tracert, Ping, Ipconfig, etc.), identify the utility and interpret the output. Objective 4.8 (N10-002.04.08)—Given a scenario, predict the impact of modifying, adding, or removing network services (e.g., DHCP, DNS, WINS, etc.) on network resources and users. Objective 4.9 (N10-002.04.09)—Given a network problem scenario, select an appropriate course of action based on a general troubleshooting strategy. Objective 4.10 (N10-002.04.10)—Given a troubleshooting scenario involving a network with a particular physical topology (i.e., bus, star/hierarchical, mesh, ring, and wireless) and including a network diagram, identify the network area affected and the cause of the problem. Objective 4.11 (N10-002.04.11)—Given a network troubleshooting scenario involving a client connectivity problem (e.g., incorrect protocol/client software/ authentication configuration, or insufficient rights/permission), identify the cause of the problem. Objective 4.12 (N10-002.04.12)—Given a network troubleshooting scenario involving a wiring/infrastructure problem, identify the cause of the problem (e.g., bad media, interference, network hardware).

Getting More Help A variety of resources are available to help you study for the Network+ Certification exam. Your options include instructor-led classes, seminars, self-paced kits, or other learning materials. To find out more about the various resources and study options for Network+ Certification, please visit the CompTIA Web site at http://www.comptia.com. To help you prepare for the CompTIA Network+ exam N10-002, Microsoft has written the Network+ Certification Training Kit. With this official self-paced training kit, you can learn the fundamentals of data networking. This kit gives you training for the real world by offering hands-on training through lessons, videos, and exercises.

O B J E C T I V E

D O M A I N

1

Media and Topologies

A data network is a collection of computers joined by a network medium that enables them to communicate. Usually, the network medium is some type of cable. Networks can use various types of media, and network technicians must be familiar with the most common ones and their properties. A topology is the way that the network uses the designated medium to connect the computers together—in other words, the physical layout of the network. The media and topologies used to build local area networks (LANs), while primarily associated with the physical (or bottom-most) layer of the Open Systems Interconnection (OSI) reference model, are also intimately connected with the protocols that operate at the second layer of the model, called the data-link layer. An understanding of network media and topologies is meaningless without an understanding of the protocols that use them. Most of the commonly used data-link layer protocols can use various types of media and topologies. The standards on which the protocols are based contain physical layer specifications that include cable types and installation guidelines, such as topologies and maximum cable lengths. LANs consist of more than just computers and cables, however. To attach a computer to the network, it must have a network interface card (NIC) in it, and to attach the cables to the NICs, they must have connectors on them. In addition, some network topologies require other hardware elements, such as hubs. More complicated network installations consist of multiple LANs connected using devices such as bridges, routers, switches, gateways, or even wide area network (WAN) links. You must understand the functions of all of these components and devices, and this objective domain tests your knowledge of them.

Tested Skills and Suggested Practices The skills that you need to successfully master the Media and Topologies objective domain on the Network+ Certification exam include:

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Recognizing the following logical or physical network topologies given a schematic diagram or description: bus, ring, star/hierarchical, mesh, and wireless. Practice 1: Study the specifications associated with the various networking protocols that use these topologies, including Ethernet (IEEE 802.3), Token Ring (IEEE 802.5), and wireless LANs (IEEE 802.11b) and learn which topologies are used by each protocol and cable type. Practice 2: Create diagrams of simple LANs that use each of the specified topologies and compare them with any test or lab networks you have access to. Identify which topology your network uses. Specifying the main features, including speed, access method, topology, and media of: IEEE 802.3 (Ethernet), IEEE 802.5 (Token Ring), IEEE 802.11b (wireless), and FDDI networking technologies. Practice 1: Study the specifications for these protocols. The protocol standards specify the basic functions of the protocols, such as their speeds and access methods. List the various media and topologies you can use with each one. Practice 2: Determine which of the specified protocols your network uses. Examine the hardware used to construct it (after obtaining permission from the network administrator) and determine how it was installed. Specifying the characteristics, such as speed, length, topology, and cable type, of the following IEEE 802.3 (Ethernet) standards: 10BASE-T, 100BASE-TX, 10BASE2, 10BASE5, 100BASE-FX, and Gigabit Ethernet. Practice 1: Study the specifications for the various Ethernet physical layer options and compare their relative advantages in transmission speed, topology, and cable lengths. Practice 2: Create a diagram of your network’s physical layer by studying the hardware used to construct it and determining how it was installed. Measure the lengths of the cable segments, mark them on your diagram, and determine whether your network was installed according to the specifications for the standard it uses. Recognizing the following media connectors and describing their uses: RJ-11, RJ-45, AUI, BNC, ST, and SC. Practice 1: Create a list of the various connectors used to build LANs and specify the protocol and network medium that uses each one. Practice 2: Obtain cables that use each of the connectors on your list and take them apart, examining how they are constructed and how the conductors are connected.

Objective Domain 1

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Choosing the appropriate media type and connectors to add a client to an existing network. Practice 1: Select a familiar business or organization. Make a list of its networking needs, including elements such as the number of computers it requires, the distances between them, the environmental conditions in which they would be installed, and the amount of data they have to transfer. Compare these requirements with the capabilities of the various media types and connectors used by the common data-link layer protocols. Select the one best suited to the job. Practice 2: Determine which media type and connectors your network uses and then redesign it using the other available media types and connectors. Estimate whether the redesigned network would be an improvement, based on criteria such as network performance, tolerance of cable breaks, and other physical layer faults. Describing the purpose, features, and functions of the following network components: hubs, switches, bridges, routers, gateways, CSU/DSUs, NICs/ISDN adapters/system area network cards, wireless access points, and modems. Practice 1: Study the functions of each of these devices and determine if they are currently used on your network. For each device your network is not using, determine how you would integrate it and what purpose it could possibly serve. Practice 2: Obtain product literature for several examples of each of these devices (from manufacturers, printed catalogs, or the World Wide Web) and familiarize yourself with their general appearance and common features.

Further Reading This section lists supplemental readings by objective. We recommend that you study these sources thoroughly before taking this exam.

Objective 1.1 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 1 in Chapter 2, “Network Hardware.” Microsoft Corporation. Microsoft Encyclopedia of Networking. Redmond, Washington: Microsoft Press, 2000. See entries for “bus topology,” “mesh topology,” “ring topology,” “star bus topology,” “star topology,” and “topology.”

Objective 1.2 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lessons 1, 2, 3, and 5 in Chapter 5, “Data-Link Layer Protocols.”

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Readiness Review—Exam N10-002 Microsoft Corporation. Microsoft Encyclopedia of Networking. Redmond, Washington: Microsoft Press, 2000. See entries for “Ethernet,” “Fiber Distributed Data Interface,” “Token Ring,” and “wireless networking.”

Objective 1.3 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 1 in Chapter 5, “Data-Link Layer Protocols.” Spurgeon, Charles. “Quick Reference Guides to 10 Mbps Ethernet” and “Quick Reference Guides to 100 Mbps Ethernet.” These documents are available on Charles Spurgeon’s Web site at http://wwwhost.ots.utexas.edu/ethernet/ethernet-home.html.

Objective 1.4 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lessons 1 in Chapter 2, “Network Hardware.” Connectivity Knowledge Platform. “Connector Reference Chart.” This document is available on CKB’s Web site at http://www.mouse.demon.nl/ckp/misc/conchart.htm.

Objective 1.5 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 1 in Chapter 14, “Planning the Network.” Microsoft Corporation. Microsoft Encyclopedia of Networking. Redmond, Washington: Microsoft Press, 2000. See entries for “cabling,” “coaxial cabling,” “fiber optic cabling,” “twisted pair cabling,” and “unshielded twisted pair (UTP) cabling.”

Objective 1.6 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lessons 1, 2, and 3 in Chapter 3, “Network Connections,” Lesson 2 in Chapter 2, “Network Hardware,” Lesson 5 in Chapter 5, “Data-Link Layer Protocols,” and Lesson 2 in Chapter 12, “Remote Network Access.” University of Western Ontario. “Bridges vs. Switches vs. Routers.” This comparison table is available on the UWO Web site at http://www.csd.uwo.ca/courses/CS457a/ reports/handin/efteevan/A1/compare.html. Microsoft Corporation. Microsoft Encyclopedia of Networking. Redmond, Washington: Microsoft Press, 2000. See entries for “access point,” “bridge,” “Channel Service Unit/ Data Service Unit (CSU/DSU),” “gateway,” “hub,” “Integrated Services Digital Network (ISDN),” “modem,” “network interface card (NIC),” “router,” “switch,” and “wireless networking.”

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O B J E C T I V E

1 . 1

Recognize the following logical or physical network topologies given a schematic diagram or description: star/hierarchical, bus, mesh, ring, wireless.

Despite some sources that use topology synonymously with the term protocol, as in the “Ethernet topology” or “Token Ring” topology, a network’s topology is actually the pattern used to connect the network medium to the computers and other components. An Ethernet network can use any one of several topologies, depending on the medium you choose. The topology used to construct a network is always determined by the network medium the network uses, and the network medium you select depends on the data-link layer protocol you select. You can’t just select any cable type to use with a specific protocol and then select any topology for that cable. An Ethernet network, for example, can use any one of three different cable types: coaxial, unshielded twisted pair (UTP), and fiber optic, and each cable type is associated with a specific topology. Coaxial cable uses a bus topology, and UTP and fiber optic use a star topology. There are three main topologies associated with local area networking, and two others listed here that are seen less often.

Bus topology—A bus topology is one in which each computer on the network is connected to the next one, forming an unbroken chain with two endpoints. When a computer transmits its data, the signals travel in both directions on the bus until they reach both ends. At each end of the bus you must have a terminator, which is an array of resistors that nullifies the signals reaching it. Without the terminators, the signals reaching the ends of the bus reflect back in the other direction, interfering with the new signals being introduced and causing data loss. Bus networks are also intolerant of cabling faults or network interface failures; a break in the bus splits the network into two halves that cannot communicate with each other. The bus topology is used by the two Ethernet coaxial cable specifications, which are called Thick Ethernet (10Base5) and Thin Ethernet (10Base2).

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Ring topology—A ring topology is one in which each computer on the network is connected to the next one, as in a bus topology, but the two ends are joined to form a ring. On a ring network, the signals travel in only one direction, and the computer that transmits data is also responsible for removing it from the network after it has traversed the entire ring. In most networks using ring topology, the ring is implemented logically, not physically. The cables connecting the computers do not run directly from node to node because a single cable break would bring the entire network down. Instead, they run to a special hub called a multistation access unit (MAU or MSAU). This unit implements the ring internally by transmitting incoming signals out through each port in succession and waiting for the signal to be returned over that port by the computer before transmitting it out to the next one. The result is a logical ring topology that is more fault tolerant than a physical one because the MAU can bypass specific ports, effectively removing malfunctioning nodes from the ring. The ring topology is used by several protocols, including Token Ring and Fiber Distributed Data Interface (FDDI). Star/hierarchical topology—A star topology is one in which each of the network nodes is connected to a central cabling nexus called a hub or concentrator. The hub takes the signals arriving through any of its ports, amplifies them, and immediately transmits them out through all of its other ports. This enables the computers connected to the hub to share a single network medium, just as if they were connected with a single cable. The hub also provides greater fault tolerance than a bus network. If a cable break or a NIC failure occurs, only one computer is affected. All of the others continue operating normally. To expand a star network beyond the capacity of a single hub, you can connect an additional hub by plugging it into the existing hub’s uplink port. This expandability is not unlimited, however; the protocols that use this topology specify how many layers are permitted in the hierarchy. A network of this type is said to use a hierarchical star topology. 10Base-T Ethernet networks use the star topology, as do all Fast Ethernet networks. Mesh topology—In local area networking, a mesh topology is a theoretical construct in which each computer on the network has a dedicated connection to every other computer. This eliminates the shared medium from the LAN and enables the computers to communicate with each other at full speed, any time. The mesh topology is not feasible on today’s LANs because it requires each computer to have multiple network interfaces—one for each of the other computers on the network. The term mesh is also used in internetworking to refer to a network with redundant routes between network intersections, enabling traffic to reach a destination using any one of several paths as a fault tolerance measure. Wireless topology—Wireless LANs eliminate the need for cables as a network medium, and in doing so, eliminate the need for a standard topology. A wireless LAN typically consists of a transceiver unit, called a wireless access point, that is connected to servers or directly to the network and other devices using a standard cabled network protocol, such as Ethernet or Token Ring. Client computers with their own transceivers can then communicate with the network-attached transceiver using any one of several wireless media, such as infrared light or radio waves.

Objective 1.1

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Objective 1.1 Questions N10-002.01.01.001 A company with a 25-node Thin Ethernet network is planning to upgrade to Fast Ethernet using UTP cable. Which of the following topology changes must they make during the upgrade process? A. Bus to ring B. Ring to star C. Bus to star D. Mesh to ring

N10-002.01.01.002 A maintenance worker accidentally cuts through a LAN cable while working inside an office’s drop ceiling. On which type of topology is the cable break likely to cause the greatest disturbance in network communications? A. Bus B. Ring C. Star D. Hierarchical star

N10-002.01.01.003 Which of the following statements about hubs and MAUs are true? (Choose two.) A. Hubs amplify incoming signals before transmitting them. B. Hubs provide termination for cable segments. C. MAUs are responsible for removing signals from the ring. D. MAUs maintain network integrity by removing malfunctioning nodes from the ring.

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N10-002.01.01.004 Which of the following LAN topologies is implemented logically and not physically? A. Star B. Bus C. Mesh D. Ring

Objective 1.1 Answers N10-002.01.01.001

Correct Answers: C A. Incorrect: The bus topology is indeed used by Thin Ethernet networks. The ring topology is used by Token Ring and FDDI networks among others, but it is not used by any type of Ethernet network. B. Incorrect: Thin Ethernet networks use coaxial cable, which can only be installed using the bus topology. The star topology is used by Fast Ethernet networks running over UTP cable, however. C. Correct: The company’s existing network uses Thin Ethernet, which consists of coaxial cable installed in a star topology. The new network uses Fast Ethernet, for which one of the physical layer options is UTP cable, which you always install using a star topology. D. Incorrect: The mesh topology is not used by any form of Ethernet or LAN protocol because each computer would have to have a separate network interface for each of the other computers on the network. The ring topology is not used by any form of Ethernet network.

N10-002.01.01.002

Correct Answers: A A. Correct: When a cable break occurs on a bus network, the LAN is immediately split in two, preventing the computers on one side of the break from communicating with those on the other side. In addition, the break also creates two unterminated cable segments. This lack of termination will also affect the communications between computers on the same segment, effectively disrupting the entire network.

Objective 1.1

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B. Incorrect: If a network uses a physical ring topology, a cable break would be catastrophic, preventing all communications from traversing the entire ring and from being removed from the ring by the transmitting system. This is why the ring topology is always implemented logically using the physical configuration of a star. When a cable break occurs, only the computer connected to the MAU by that cable is affected. The MAU detects the breakdown in communications with that computer and removes it from the logical ring. C. Incorrect: On a star network, each computer is connected to the hub using a separate cable. A cable break therefore affects only one of the computer/hub connections. The rest of the computers can continue to communicate normally. D. Incorrect: A hierarchical star network is similar to a regular star network in that a break in a cable connecting a computer to a hub affects only that computer. However, a break in a cable connecting two hubs is more serious. In this case, the cable break splits the network in two, preventing the computers on one hub from communicating with the computers on the other. Unlike a bus network, however, no termination is needed, so the communications between the computers connected to each hub proceed normally.

N10-002.01.01.003

Correct Answers: A and D A. Correct: A repeater is a device that amplifies signals so they can travel longer distances without suffering from signal degradation, also called attenuation. A hub’s function is to transmit data received through any one of its ports out through all of its other ports. Hubs are also called multiport repeaters because they amplify the signals before retransmitting them. B. Incorrect: Networks using a star topology do not require termination, and hubs propagate signals to the network, not remove them. C. Incorrect: Signals are removed from the ring by the computer that originally transmitted them, not by the MAU. D. Correct: The primary reason for implementing the ring topology logically (inside the MAU) is to prevent a broken cable or malfunctioning computer from disrupting communications for the entire network. MAUs do this by performing an initialization process for each attached computer, which adds it to the ring. If a malfunction occurs, the MAU can remove the computer from the ring, bypassing it internally so that no data is transmitted to it or expected from it.

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N10-002.01.01.004

Correct Answers: D A. Incorrect: The star topology gets its name from the use of a hub as the cabling nexus for all of the computers on the LAN. Even though the computers may not be dispersed evenly around a hub located in the exact center of the star, the physical layout of the network reflects the topology. B. Incorrect: The bus topology consists of computers that are physically joined by cables running in a chain from one system to the next. C. Incorrect: The mesh topology doesn’t exist on a LAN, either logically or physically; it is an internetwork topology that provides redundant physical paths between destinations. D. Correct: The ring topology is implemented logically by a MAU that transmits incoming data packets out through each one of its ports in turn, waiting for the connected computer to return the packet before proceeding to the next port. Physically, the network is cabled using a star topology.

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O B J E C T I V E

1 . 2

Specify the main features of 802.2 (LLC), 802.3 (Ethernet), 802.5 (token ring), 802.11b (wireless), and FDDI networking technologies, including speed, access method, topology, media.

The Institute of Electrical and Electronics Engineers (IEEE) is responsible for the development and maintenance of the standards governing the most popular data-link layer LAN protocols in use, including Ethernet (IEEE 802.3), Token Ring (IEEE 802.5), and one of the most popular new wireless LAN technologies, IEEE 802.11b. FDDI is another common LAN protocol that is based on American National Standards Institute (ANSI) specification X3T12. The primary features of these protocols are listed in the following table.

Standard

MAC Method

Speeds

Media

Topologies

IEEE 802.3 (Ethernet)

CSMA/CD

10 Mbps 10/100 Mbps 10/100 Mbps

Coaxial U TP Fiber optic

Bus Star Star

IEEE 802.5 (Token Ring)

Token passing

4/16 Mbps

IBM Type 1/ UTP

Ring

FDDI

Token passing

100 Mbps

Fiber optic

Double ring

IEEE 802.11b

CSMA/CA

11 Mbps

DSSS

Ad hoc infrastructure

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Readiness Review—Exam N10-002 Ethernet is the most popular data-link layer LAN protocol in the world, with millions of nodes installed. Ethernet networks can run at different speeds and use different cables and topologies, but the main identifying characteristic common to all Ethernet networks is the media access control (MAC) mechanism known as Carrier Sense Multiple Access with Collision Detection (CSMA/CD). A MAC mechanism regulates access to a network, ensuring that each computer has an opportunity to transmit its data. Each computer on a CSMA/CD Ethernet network begins the transmission process by listening to the network, and if it’s free, proceeds to transmit its data. Sometimes two computers transmit simultaneously, however, causing a collision. Collisions are a normal occurrence on Ethernet networks because the protocol design enables the computers to detect them when they occur and compensate for them by retransmitting the data. Over its 25-year history, Ethernet has evolved considerably. It now supports a variety of physical layer options, including two types of coaxial cable running at 10 Mbps in a bus topology; UTP cable running at 10, 100, or 1,000 Mbps in a star topology; and fiber optic cable, also running at 10, 100, or 1,000 Mbps in a star topology. Token Ring is a data-link layer protocol, developed by IBM and later standardized by the IEEE, that is fundamentally different than Ethernet. Token Ring networks all use a logical ring topology, although their physical configuration is that of a star. Token Ring’s MAC mechanism is called token passing, and it is the reason for using of the ring topology. A special packet called a token circulates around the ring until a computer has data to transmit. This computer takes possession of the token and proceeds to transmit its data. Only the computer possessing the token can transmit, making it impossible for collisions to occur on a network that is functioning properly. After the data circulates around the ring, the transmitting system is responsible for removing it from the network and generating a new token. Token Ring networks originally ran at 4 Mbps and used a shielded twisted pair (STP) cabling system called IBM Type 1. Today, virtually all Token Ring installations run at 16 Mbps and use standard UTP cables. FDDI is a 100 Mbps data-link layer protocol that was designed for network backbones that require high speeds and must span long distances. FDDI pre-dates Fast Ethernet (which has since largely replaced it), and at the time of its conception was the only 100 Mbps LAN protocol available commercially. FDDI uses the token passing MAC mechanism and the ring topology, much like Token Ring, except that in some cases, FDDI networks are physically cabled in a ring formation. The physical ring doesn’t provide the fault tolerance of the logical ring, so the standard also defines the use of an optional double ring topology. In the double ring, traffic travels in opposite directions on the two rings and the computers are connected to both rings. If one ring gets broken, the other can still carry traffic to any destination on the network.

Objective 1.2

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IEEE 802.11b is a wireless LAN standard that provides 11, 5.5, 2, and 1 Mbps transmission rates using a radio medium called Direct Sequence Spread Spectrum (DSSS). Wireless protocols obviously don’t have topologies in the usual sense of the word, but IEEE 802.11b supports two different arrangements that can be called topologies. An ad hoc network is one in which a group of computers all using the IEEE 802.11b protocol communicate with each other as peers. An infrastructure network is one in which the wireless computers communicate with network access points that are connected to a traditional LAN using cables. The MAC mechanism the IEEE 802.11b uses is called Carrier Sense Multiple Access with CollisionAvoidance (CSMA/CA). CSMA/CA is a variation on the CSMA/CD mechanism used on Ethernet networks. On a CSMA/ CA network, computers still listen to the network to see if it is free before transmitting their data. After a computer transmits its data, the receiving system performs a cyclical redundancy check (CRC) verification on the incoming frame and returns an acknowledgment message to the sender if it doesn’t detect any errors. Using an acknowledgment message replaces the collision detection mechanism used on CSMA/CD networks.

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Objective 1.2 Questions N10-002.01.02.001 Which of the following protocol/medium combinations use CSMA/CD as their MAC mechanism? (Choose two.) A. Ethernet/Coaxial B. Token Ring/UTP C. Ethernet/UTP D. FDDI/Fiber optic E. IEEE 802.11b/DSSS

N10-002.01.02.002 Which of the following protocols is capable of transmitting data at 10, 100, or 1,000 Mbps? A. Ethernet B. Token Ring C. FDDI D. IEEE 802.11b

N10-002.01.02.003 Which of the following protocols can be installed using a physical ring topology? A. Ethernet B. Token Ring C. FDDI D. IEEE 802.11b

Objective 1.2

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Correct Answers: A and C A. Correct: All Ethernet networks use the CSMA/CD MAC mechanism, no matter what type of cable. B. Incorrect: Virtually all of the Token Ring networks installed today use standard UTP cables and the token passing MAC mechanism. C. Correct: The CSMA/CD MAC mechanism is the identifying characteristic of an Ethernet network, no matter which cable type it uses. D. Incorrect: FDDI networks can use a standard ring or a double ring topology, but they all use the token passing MAC mechanism. E. Incorrect: The IEEE 802.11b standard calls for a CSMA/CA MAC mechanism, not CSMA/CD.

N10-002.01.02.002

Correct Answers: A A. Correct: Standard Ethernet networks run at 10 Mbps, Fast Ethernet networks run at 100 Mbps, and Gigabit Ethernet networks run at 1,000 Mbps (1 Gbps). B. Incorrect: Token Ring networks can run at 4 or 16 Mbps only. C. Incorrect: FDDI networks run at 100 Mbps only. D. Incorrect: IEEE 802.11b networks run at a maximum speed of 11 Mbps, with fallback speeds of 5.5, 2, and 1 Mbps.

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N10-002.01.02.003

Correct Answers: C A. Incorrect: Ethernet networks are always installed using either a bus or star topology. The protocol could not work on a ring because it would have no means of removing transmitted signals from the cable. B. Incorrect: Token Ring networks use a ring topology, but it is not a physical ring. Physically, the network is installed using a star topology, and a logical ring topology is implemented inside the Token Ring MAU. C. Correct: FDDI uses a ring topology that can conceivably be installed as a physical ring. On physical ring FDDI networks, using a double ring is recommended to provide fault tolerance. D. Incorrect: The IEEE 802.11b protocol does not use any of the standard LAN topologies, including the ring.

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O B J E C T I V E

1 . 3

Specify the characteristics (e.g., speed, length, topology, cable type, etc.) of the following: 802.3 (Ethernet) standards, 10BASE-T, 100BASE-TX, 10BASE2, 10BASE5, 100BASE-FX, Gigabit Ethernet.

The IEEE 802.3 protocol (commonly known as Ethernet) is the oldest of the data-link layer protocols still used. In its 25-year history, the protocol has evolved and now there are many different variations on it running at different speeds and using different types of media. These variations have two primary elements in common: the CSMA/CD MAC mechanism and the Ethernet frame format. The most common Ethernet variants are listed in the following table. Common Name/ Physical Layer Standard

Speed

Cable Type/ Topology

Maximum Segment Length

Thick Ethernet (10Base5)

10 Mbps

RG-8 coaxial (bus)

500 meters

Thin Ethernet (10Base2)

10 Mbps

RG-58 coaxial (bus)

185 meters

Ethernet (10Base-T)

10 Mbps

Cat 3 UTP (star)

100 meters

Fast Ethernet (100Base-TX)

100 Mbps

Cat 5 UTP (star)

100 meters

Fast Ethernet (100Base-T4)

100 Mbps

Cat 3 UTP (star)

100 meters

Fast Ethernet (100Base-FX)

100 Mbps

62.5/125-multimode fiber optic (star)

412 meters

Gigabit Ethernet (1000Base-T)

1,000 Mbps

Cat 5 UTP (star)

100 meters

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Readiness Review—Exam N10-002 The various types of Ethernet are often referred to by their generic names, such as standard Ethernet, Fast Ethernet, and Gigabit Ethernet, but there are also abbreviations for the various physical layer specifications that Ethernet supports, which are more precise and commonly used. The format for these abbreviations consists of three parts, which specify network speed, the type of signaling, and either the maximum cable segment length or the type of cable used. 10Base5, the abbreviation used for Thick Ethernet, indicates that this type of network runs at 10 Mbps, uses baseband signaling, and supports a maximum cable segment length of 500 meters. Thick Ethernet networks use a type of coaxial cable called RG-8, which is relatively thick (0.405 inches), installed in a bus topology. The coaxial cable trunk can be up to 500 meters long. Each computer is connected to the trunk using a separate cable called an Attachment Unit Interface (AUI) cable, which can be up to 50 meters long. 10Base2, also known as Thin Ethernet, uses a different type of coaxial cable called RG-58, which is also installed in a bus topology. Because it’s thinner (0.195 inches), RG-58 is more flexible and easier to install than RG-8. As a result, there is no need for AUI cables on this type of network, and the trunk cable runs right up to each computer’s network interface adapter. Thin Ethernet also runs at 10 Mbps and uses baseband signaling (as do all of the Ethernet variants discussed here). The number 2 in the abbreviation 10Base2 suggests that the maximum allowable cable segment for a Thin Ethernet network is 200 meters. However, the specification actually limits the segment length to 185 meters. 10Base-T is the first Ethernet version to use UTP cable, which is installed in a star topology instead of a bus. 10Base-T runs at 10 Mbps, just like the coaxial standards, and uses baseband signaling. The letter T in 10Base-T signifies the twisted pair cable. A 10Base-T network can use any UTP cable that is Category 3 or higher, and each cable segment connecting a computer (or other device) to the hub can be up to 100 meters long. All three of the 10 Mbps Ethernet specifications listed here are defined in the IEEE 802.3 standard.

Objective 1.3

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100Base-TX is the most popular of the Fast Ethernet physical layer specifications, all of which are defined in the IEEE 802.3u standard and are known collectively as 100Base-T. Running at 100 Mbps, a 100Base-TX network uses Category 5 UTP cable installed in a star topology with cable segments up to 100 meters long. Like 10Base-T, 100Base-TX uses only two of the four wire pairs in the UTP cable and provides greater speed because of the higher quality of Category 5 cable. 100Base-T4 is a Fast Ethernet specification intended to be an upgrade path for 10Base-T networks using Category 3 UTP cable. Like 100Base-TX, 100Base-T4 runs at 100 Mbps and is installed in a star topology with segments up to 100 meters long. To run at higher speeds on Category 3 cable, 100Base-T4 uses all four of the wire pairs in the cable. Two are dedicated transmit and receive pairs, as in 10Base-T and 100Base-TX. The other two pairs are bidirectional, carrying traffic in either direction as needed. 100Base-FX is a Fast Ethernet specification that uses fiber optic cable instead of UTP. The network runs at the same speed as 100Base-TX and 100Base-T4—100 Mbps—and uses the same star topology. But the 62.5/125-micron multimode fiber optic cable can have segments as long as 412 meters because of its resistance to attenuation. When running in full duplex mode, 100Base-FX cable segments can be up to 2 kilometers (2,000 meters) long. Gigabit Ethernet is the latest form of Ethernet. It increases a network’s transfer speed to 1,000 Mbps. Although most of the physical layer specifications for Gigabit Ethernet call for fiber optic cable, there is one standard, IEEE 802.3ab, that calls for Category 5 UTP cable installed in a star topology with a maximum segment length of 100 meters. This standard is referred to as 1000Base-T. To achieve this speed using standard Category 5 cable, 1000Base-T uses all four pairs of wires bidirectionally.

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Objective 1.3 Questions N10-002.01.03.001 You are designing a single LAN that consists of 25 computers scattered around a building. The two most distant computers are 200 meters away from each other. Which of the following Ethernet physical layer specifications can you be certain will operate successfully? (Choose four.) A. 10Base2 B. 10Base5 C. 10Base-T D. 100Base-FX E. 100Base-TX

N10-002.01.03.002 Which of the following Ethernet physical layer specifications are designed to run on Category 3 UTP cable? (Choose two.) A. 10Base2 B. 10Base-T C. 100Base-TX D. 100Base-T4 E. 1000Base-T

N10-002.01.03.003 What distinguishes the 100Base-FX physical layer specification from the other Fast Ethernet specifications? A. 100Base-FX transmits data at higher speeds than the other Fast Ethernet specifications. B. 100Base-FX uses a different topology from the other Fast Ethernet specifications. C. 100Base-FX has a greater maximum segment length than the other Fast Ethernet specifications. D. 100Base-FX is defined in a different standard document than the other Fast Ethernet specifications.

Objective 1.3

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N10-002.01.03.004 A new tenant is moving into office space that is already wired with Category 5 UTP cable in a star topology with no segments longer than 100 meters. Which of the following Ethernet physical layer specifications can the tenant use to build the fastest possible network without installing new cable? A. 10Base-T B. 100Base-T4 C. 100Base-TX D. 1000Base-T


Correct Answers: B, C, D, and E A. Incorrect: A 10Base2 (Thin Ethernet) network has a maximum cable segment length of 185 meters, despite the implication of the number 2 in its abbreviation. A 200-meter-long segment connecting the most distant computers would be too long and may not function properly. B. Correct: A 10Base5 (Thick Ethernet) network can have a cable segment up to 500 meters long, which is easily enough to connect the two most distant computers. C. Correct: The 10Base-T specification calls for cable segments up to 100 meters long, but when you use the star topology on an Ethernet network, the hub functions as a multiport repeater. Because the hub repeats the signals passing through it, each cable connecting a computer to the hub can be the maximum length of 100 meters. This enables you to connect two computers that are 200 meters apart. D. Correct: The 100Base-FX specification permits the fiber optic cables to be as long as 412 meters, more than sufficient to connect the two distant computers. E. Correct: Although a 100Base-TX network runs at 10 times the speed of 10Base-T, the fact that the protocol specification calls for Category 5 UTP cable enables the segments to be 100 meters long. Because 100Base-TX uses a star topology like 10Base-T does, the repeating hub enables the maximum distance between two computers to be 200 meters.

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N10-002.01.03.002

Correct Answers: B and D A. Incorrect: 10Base2, otherwise known as Thin Ethernet, runs on coaxial cable only. B. Correct: The 10Base-T physical layer standard was developed at a time when most of the UTP cable being installed conformed to the Category 3 specification. This means that you can run 10Base-T on almost any UTP cable network you find today. C. Incorrect: The 100Base-TX standard uses the same star topology and cable segment lengths as 10Base-T, as well as the same two wire pairs inside the cable, but it transmits data 10 times faster. As a result, 100Base-TX will not function properly on a Category 3 UTP network. D. Correct: The 100Base-T4 standard was specifically developed to be an upgrade path for existing 10Base-T networks running on Category 3 UTP cable. Like 100Base-TX, 100Base-T4 runs at 100 Mbps and supports 100 meter segments. What makes it possible for a Category 3 UTP network to run at 100 Mbps is that 100Base-T4 uses all four pairs of wires in the cable. E. Incorrect: Gigabit Ethernet networks run at 1,000 Mbps. Although the 1000Base-T standard uses UTP cable with a maximum segment length of 100 meters, like 10Base-T and 100Base-TX, the faster protocol stretches the limits of the UTP cable’s capabilities. Category 5 is the minimum for a 1000Base-T network; Category 3 will not function properly with this protocol.

N10-002.01.03.003

Correct Answers: C A. Incorrect: All of the Fast Ethernet physical layer specifications, including 100Base-FX, transmit data at 100 Mbps. B. Incorrect: All of the Fast Ethernet physical layer specifications, including 100Base-FX, use the star topology. C. Correct: The 100Base-FX specification calls for 62.5/125-multimode fiber optic cable, which supports segment lengths of up to 412 meters, more than five times that of the copper-based Fast Ethernet specifications. D. Incorrect: All of the Fast Ethernet physical layer specifications, including 100Base-FX, are defined in the IEEE 802.3u document.

Objective 1.3

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N10-002.01.03.004

Correct Answers: D A. Incorrect: It is possible to install a 10Base-T network using existing Category 5 UTP cable, but Fast Ethernet and Gigabit Ethernet specifications would run faster. B. Incorrect: The 100Base-T4 specification is designed for use with Category 3 UTP cable, but it would run perfectly well on Category 5. However, 100Base-TX runs more efficiently on Category 5 and 100Base-T runs on Category 5 cable at 1,000 Mbps—10 times the speed of 100Base-T4. C. Incorrect: The 100Base-TX specification calls for Category 5 UTP cable, as does the 1000Base-T specification, which runs 10 times faster. D. Correct: The 1000Base-T specification is designed to run at 1 Gbps on the same type of cable installation as 100Base-TX, Category 5 UTP, using a star topology, and 100 meter maximum segments.

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O B J E C T I V E

1 . 4

Recognize the following media connectors and/or describe their uses: RJ-11, RJ-45, AUI, BNC, ST, SC.

The different types of cables used to build LANs use several different types of connectors to attach to computers, hubs, and other devices. The connector type is associated with a specific type of cable. Thick Ethernet (10Base5) networks use N connectors to join lengths of RG-8 cable, but to connect a computer to the network, use an Attachment Unit Interface (AUI) cable that runs from a special connector, called a transceiver, on the coaxial trunk to an AUI connector on the computer’s network interface adapter. The AUI connector on the network adapter is a 15-pin, female, D-shell connector with two rows of eight pins and seven pins, respectively, not to be confused with a similar connector sometimes used for connecting a joystick to a computer. Since Thick Ethernet is almost never used today, AUI connectors are becoming increasingly rare. The standard 15-pin, VGA video connector has three rows of five pins each, the parallel port uses a 25-pin, female, D-shell connector called a DB-25, and the serial ports are male connectors with either nine or 25 pins, called DB-9 or DB-25. Thin Ethernet (10Base2) networks use BNC (Bayonet Neil-Concelman) connectors for all of their coaxial cable connections. The BNC connector on a network interface adapter is a round, male plug with a single pin in the center and two detents on the sides, called slots, that inserts into a female BNC socket connector with two keys, called pins, corresponding to the detents. A twist of the female component locks the two halves together. 10Base2 network interface adapters have male BNC connectors to which you connect a T fitting that has one female and two male connectors on it. With the T in place, you attach two RG-58 cables to the male connectors on the crossbar of the T. These cables run to the T connectors on either side of the computers. This configuration enables you to create the bus topology the Thin Ethernet standard requires.

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Readiness Review—Exam N10-002 UTP cable networks, such as those running 10Base-T, 100Base-TX, 100Base-T4, and 1000Base-T Ethernet, all use a modular connector called an RJ-45. This is a rectangular, eight-pin connector that is similar in construction and appearance to the four- or six-pin RJ-11 connector used on the telephone network. Each of the wires in a UTP cable is attached to one of the pins in the connector. Network interface adapters and hubs on UTP networks have female RJ-45 connectors, to which you connect UTP cables with male RJ-45 connectors on both ends. It’s vital that you don’t confuse the smaller RJ-11 connectors with RJ-45 connectors. A standard telephone cable with RJ-11 connectors can plug into the female RJ-45 connectors in a network adapter or hub, but telephone cables are not designed to carry data traffic and will not function properly on a computer network. Fiber optic networks, such as 100Base-FX Ethernet, typically use one of two connector types. The straight tip (ST) connector is round, with one central pin and detents and keys to lock the male and female halves together, much like a BNC connector. Fiber optic cables have male ST connectors that plug into the corresponding female connectors on network interface adapters and hubs. Fiber optic cables are often installed in a duplex configuration that uses two separate connectors of each gender. The other type of fiber optic connector, called a subscriber connector (SC), is square and locks in place simply by inserting the male half on the cable into the female half on the adapter or hub.

Objective 1.4

Objective 1.4 Questions N10-002.01.04.001 Which type of Ethernet network uses the connector shown in the image? Examine the connector shown in the image below. Examine the connector shown in the Exhibit.

f01cn01.jpg

A. 10Base2 B. 100Base-T4 C. 100Base-FX D. 1000Base-T

N10-002.01.04.002 Which types of cable connector are associated with coaxial cables? (Choose two.) A. RG-8 B. AUI C. ST D. RJ-11 E. BNC

N10-002.01.04.003 Which of the following connectors has the same number of pins as an AUI connector? A. BNC B. RJ-11 C. VGA D. DB-25

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Correct Answers: A A. Correct: The figure shows a T fitting attached to two coaxial cables using BNC connectors. 10Base2 (Thin Ethernet) is the only form of Ethernet that uses these connectors. B. Incorrect: The 100Base-T4 physical layer specification calls for UTP cable, which uses RJ-45 connectors, not the BNC connectors shown in the image. C. Incorrect: The 100Base-FX physical layer specification calls for fiber optic cable, which uses ST or SC connectors, not the BNC connectors shown in the image. D. Incorrect: The 1000Base-T physical layer specification calls for UTP cable, which uses RJ-45 connectors, not the BNC connectors shown in the image.

N10-002.01.04.002

Correct Answers: B and E A. Incorrect: RG-8 is not the name of a connector; it is the name of the coaxial cable used to build Thin Ethernet (10Base2) networks. B. Correct: You use AUI connectors on Thick Ethernet (10Base5) network interface adapters, with an AUI cable, to connect a computer to a coaxial cable trunk, using a transceiver. C. Incorrect: ST connectors attach fiber optic cables to network interface adapters and hubs. They are never used with coaxial cable. D. Incorrect: RJ-11s are the four- or six-pin connectors found on telephone equipment. They are not used for data networking and never with coaxial cable. E. Correct: BNC connectors are used on Thin Ethernet (10Base2) networks to connect coaxial cables to the network interface adapters installed in the computers.

Objective 1.4

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N10-002.01.04.003

Correct Answers: C A. Incorrect: A BNC connector has only one pin, and an AUI connector has 15. B. Incorrect: The RJ-11 connector has either four or six pins, and an AUI connector has 15. C. Correct: The VGA connector used to attach a monitor to a computer has 15 pins, just like an AUI connector. However, the two are easily distinguishable because the VGA connector has three rows of five pins each and the AUI connector has two rows: one of eight pins and one of seven. D. Incorrect: The DB-25 connector used for a computer’s parallel and serial ports has the same D-shell configuration as an AUI connector, but the DB-25 has 25 pins, and the AUI connector has 15.


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O B J E C T I V E

1 . 5

Choose the appropriate media type and connectors to add a client to an existing network.

When selecting an appropriate network medium for a LAN installation, there are several factors you must consider, including the following:

Segment length—The distances between the computers you intend to connect are an important factor in the medium selection process. In a network using a bus topology, such as Thick Ethernet or Thin Ethernet, the maximum segment length reflects the distance between the two terminated computers that form the ends of the bus. For most star networks, the maximum segment length is the distance between each computer and the hub, because an Ethernet hub also functions as a repeater. As a result, hub placement is also an important aspect of planning a star network. Exceeding the maximum segment length specified by the protocol standard can affect the network’s performance in several ways. A segment that is too long can cause signals to attenuate to the point that the receiving computer cannot read them. On an Ethernet network, excessively long segments can prevent the protocol from detecting packet collisions when they occur. Upgradability—The cable you select for a network must certainly support the physical layer specification for the protocol you intend to use right now, but you should also consider your future plans and whether you may want to upgrade your network in the future. The combination of the cable, the connectors and other hardware, and the labor needed to install them can represent one of the most costly elements of the network, one that you probably don’t want to repeat a few years from now. This is especially true when a modest additional expenditure now can provide you with an upgrade path that stretches far into the future. This lack of an upgrade path is one of the primary reasons that Ethernet networks using coaxial cable are all but unheard of today. For UTP networks, you should install nothing less than Category 5 cable. If you even remotely suspect that Gigabit Ethernet may be in your future, you may want to consider Category 5e or one of the higher performance cables on the market.

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Fault tolerance—The degree to which a network is tolerant of cable breaks and faulty connectors is determined more by the network topology than by the cable’s properties. Another reason for the demise of coaxial-based Ethernet networks is the bus topology. A break anywhere along the length of the bus prevents all of the computers on the network from communicating. Star networks are inherently more tolerant of cable faults (as are logical ring networks wired physically as stars) and are the current industry standard. Ease of installation—Some cables are easier to install than others, and the labor costs for a difficult installation can have a great effect on the overall price of the network. UTP is by far the easiest and most economical to install of the standard cable types, especially because there are a great many telephone cable installers with the expertise needed. Coaxial cables are thicker than UTP and relatively inflexible, making it more difficult to install than UTP, but the basic principles are the same because both are copper-based electrical cables. Fiber optic cable, on the other hand, is based on optical, not electrical, signals, and virtually everything about the installation, including the components, the tools, and the skills needed, is more complicated than that of a copper cable installation. Environmental factors—In some cases, the environmental conditions at the site where the network is to be installed can affect your cable selection. For example, electric motors, heavy equipment, and other sources of electromagnetic interference can make a copper cable installation impractical, but fiber optic cable can perform under these conditions without a problem. You must also consider the building codes in your area, which may force you to use plenum-rated cables or to install your cables in a certain way. If you have to connect computers in different buildings, only fiber optic cable can keep the two structures electrically isolated while maintaining data communications.

Objective 1.5

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Objective 1.5 Questions N10-002.01.05.001 A company with 20 standalone computers engaged a network consultant to join them into a LAN. The company has elected to use the Ethernet protocol at the data-link layer. The consultant left the project after designing a network for the company but before installing it, and the job is now being offered to you. The computers are divided among several work areas in a large manufacturing plant, with the two most distant machines being 175 meters away from each other. The primary goal of the installation is to connect all of the computers as a single LAN running at 10 Mbps. The secondary goals are to provide an upgrade path to 100 Mbps Fast Ethernet in the future and to provide a measure of fault tolerance so that a single cable failure will not affect the entire network. The solution provided by the first consultant is to install a Thin Ethernet LAN connecting all of the computers to a single cable segment. Which of the following statements is true about the proposed solution? A. The solution achieves neither the primary goal nor either of the secondary goals. B. The solution achieves the primary goal but neither of the secondary goals. C. The solution achieves the primary goal and one of the secondary goals. D. The solution achieves the primary goal and both of the secondary goals.

N10-002.01.05.002 Which of the following cable types do not provide an upgrade path to Fast Ethernet? A. RG-58 coaxial B. Category 3 UTP C. Category 5 UTP D. 62.5/125-multimode fiber optic

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Correct Answers: B A. Incorrect: A Thin Ethernet network will adequately support 25 computers using a cable segment up to 185 meters long, so it does achieve the primary goal. However, the speed limitation of Thin Ethernet and its bus topology prevent it from achieving either of the secondary goals. B. Correct: It is true that a Thin Ethernet network will support the company’s 25 computers at 10 Mbps, achieving the primary goal. However, the coaxial cable used by Thin Ethernet is limited to a speed of 10 Mbps, so there is no upgrade path to Fast Ethernet without installing new cable. In addition, the bus topology used by Thin Ethernet is highly sensitive to cable faults. A single break in the coaxial cable or connector failure could bring down the entire network. C. Incorrect: Thin Ethernet provides an adequate solution for the primary goal, but it cannot be upgraded to Fast Ethernet and it cannot tolerate a cable fault without affecting the entire network. Thus, neither of the secondary goals is achieved. D. Incorrect: The solution achieves the primary goal by connecting the 25 computers to a 10 Mbps LAN, but Thin Ethernet’s lack of an upgrade path or of cable fault tolerance prevents it from achieving either of the secondary goals.

N10-002.01.05.002

Correct Answers: A A. Correct: The RG-8 and RG-58 coaxial cables used for Thick and Thin Ethernet networks are not capable of transmitting data at speeds faster than 10 Mbps. Fast Ethernet runs at 100 Mbps, and therefore cannot run on coaxial cable. B. Incorrect: The 100Base-T4 Fast Ethernet physical layer specification was designed to use Category 3 cable, making it a natural upgrade path for older 10 Mbps Ethernet networks. C. Incorrect: The 100Base-TX Fast Ethernet physical layer specification is the upgrade path for networks using Category 5 UTP cable. D. Incorrect: The 100Base-FX Fast Ethernet physical layer specification is the upgrade path for networks using 62.5/125-multimode fiber optic cable.

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O B J E C T I V E

1 . 6

Identify the purpose, features, and functions of the following network components: hubs, switches, bridges, routers, gateways, CSU/ DSUs, network interface cards/ISDN adapters/ system area network cards, wireless access points, modems.

In addition to cables, networks use a variety of other hardware components, including the following:

Network interface adapters—The network interface adapter (which usually takes the form of a NIC) is the component that enables you to connect a computer to a network. The adapter is the interface between the computer’s expansion bus and the network medium, which in most cases means an expansion card that plugs into a bus slot and has a connector for a network cable. The NIC and its accompanying device driver implement the data-link layer protocol (such as Ethernet or Token Ring) and perform all of the functions associated with that protocol, including media access control, network layer data encapsulation, and error detection. ISDN adapters—Integrated Services Digital Network (ISDN) is a digital communications service that uses standard Public Switched Telephone Network (PSTN) lines, also known as the Plain Old Telephone Service (POTS), to provide high-speed WAN communications. The ISDN service is based on 64 Kbps channels that can be combined to provide transmissions at speeds up to that of a T-1. A T-1 has a capacity of 1.544 Mbps, that of 24 64-Kbps ISDN channels. An ISDN adapter is a device used to connect a computer to the ISDN service, enabling the computer to access a remote network at high speeds or to function as a router, providing remote network access to a LAN. The ISDN service requires the subscriber

36

Readiness Review—Exam N10-002 to provide a hardware device called a network termination 1 (NT1) at the cable terminus, to which you can attach terminal equipment in the form of native ISDN devices (such as ISDN telephones) or standard equipment, using a device called a terminal adapter to translate between the device’s native format and the ISDN digital format. ISDN is rarely used for standard telephone communications in the U.S., so it’s common to find ISDN adapters on the market that include both the NT1 and the terminal adapter on a single expansion card.

SAN cards—A storage area network (SAN) is a separate network dedicated to communications between servers and dedicated network storage devices. It is becoming increasingly popular to add storage capacity to enterprise networks using standalone devices, such as Redundant Array of Independent Disks (RAID) arrays and Network Attached Storage (NAS) appliances. Connecting these devices directly to the network enables multiple servers to access them, providing greater fault tolerance for network applications. However, the amount of network traffic generated by the communications between servers and storage device is substantial. Many installations now build a separate, independent, high-speed network connecting just the servers and the storage appliances. Fibre channel is the name of the protocol that has come to be associated with storage area networking, and a SAN card, also known as a Host Bus Adapter (HBA), is a fibre channel network interface adapter that connects a computer or a storage device to such a network. Hubs—A hub is a device that connects computers and other devices to a network that uses the star topology. The hub is a box with a series of ports for a particular network medium in it, and you connect each computer to one of the ports with a separate cable. The hub’s functions depend on the data-link layer protocol it supports. Ethernet hubs, also called multiport repeaters, and simple physical layer devices take all of the signals they receive through any of their ports, amplify them, and transmit them out through all of the other ports simultaneously. Token Ring hubs, called MAUs, perform more complicated functions that are needed to implement a local ring topology on a physical star network. Bridges—A bridge is a data-link layer device that joins two network segments, similar or dissimilar, and filters the traffic passing between them. Bridges maintain tables containing the hardware addresses of the computers on the two segments. When a packet arrives at the bridge, the bridge reads the destination address in the packet’s data-link layer protocol header. If the packet is destined for a computer on the other network segment, the bridge transmits it onto that segment. If the packet is destined for a computer on the same segment from which it arrived, the bridge simply discards the packet, because there is no need to forward it to the other segment. Splitting a LAN into two segments and connecting them with a bridge is a method for reducing the traffic level on a busy network while retaining the single broadcast domain that is characteristic of a LAN.

Objective 1.6

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Switches—A switch is a data-link layer device that functions much like an Ethernet hub, except that instead of forwarding incoming signals out through all of the device’s ports, the switch forwards each packet out through only one port—the one that provides access to the destination computer. Broadcast transmissions are forwarded out through all of the ports. Replacing a hub with a switch eliminates the shared medium from the network, drastically reduces the number of collisions, and provides each pair of computers with a dedicated connection using the full bandwidth of the medium. Replacing routers with switches joins separate networks into a single LAN and reduces the latency generated by the routers’ processing overhead without increasing the number of collisions. Switches are more expensive than hubs and less expensive than routers; they provide an effective upgrade path for a network that is bogged down by large amounts of traffic. Routers—A router is a network layer device that connects LANs and transfers data selectively between them.To transmit data to a computer on another network, your packets must be forwarded by routers, based on the addresses of the destination systems. Routers can take many forms, from large, expensive hardware devices located in a corporate data center to small Internet access devices to software applications running on a computer. Routers forward packets using information stored in their routing tables, which supply them with the most efficient route to a particular destination. The routing tables are typically compiled by the routers using specialized routing protocols. On a large internetwork such as the Internet, packets may be passed along by many different routers on the way to their destinations. Gateways—A gateway is an application layer device that provides a link between two networks in a highly specific manner. For example, an e-mail gateway enables two separate e-mail systems to communicate with each other. A gateway can consist of hardware, software, or both. (Note that the term gateway is also used in Transmission Control Protocol/Internet Protocol (TCP/IP) parlance as a synonym for router.) Modems—A modem (modulator/demodulator) is a device that converts signals between digital and analog formats so they can be transmitted over a standard PSTN line. Computers are digital devices and the PSTN is analog, so the modem on the sending end converts the computer’s digital data to analog signals before transmitting them. When the analog signals reach the other end of the connection, the modem there converts them back into digital form so the receiving computer can use them. CSU/DSUs—A Channel Service Unit/Data Service Unit (CSU/DSU) is the device that functions as the terminus at each end of a leased telephone line, such as a T-1 or a T-3. The protective and diagnostic functions of the CSU/DSU are similar to those of a modem, except that in most cases, leased lines are digital, so there is no analog/ digital conversion necessary.

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Objective 1.6 Questions N10-002.01.06.001 A switch functions at which layer of the OSI reference model? A. Physical B. Data-link C. Network D. Application

N10-002.01.06.002 To relieve the performance degradation experienced by users of a highly-trafficked 50-node LAN, you decide to split the network into two separate segments. Which of the following devices enables you to connect the two segments and still maintain a single LAN? (Choose two.) A. A bridge B. A switch C. A router D. A gateway

N10-002.01.06.003 Which of the following devices is always used to transmit data between computers in analog form? A. An ISDN adapter B. A SAN adapter C. A modem D. A CSU/DSU

Objective 1.6

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N10-002.01.06.004 Which of the following modifications will produce a nonfunctioning network? A. Replacing hubs with switches B. Replacing hubs with routers C. Replacing bridges with routers D. Replacing routers with switches


Correct Answers: B A. Incorrect: Physical layer devices, such as hubs, work only with raw signals, such as electrical voltages, and do not interpret the signals into data. B. Correct: Switches function at the data-link layer by examining the destination address in a packet’s data-link layer protocol header and forwarding the packet out through the port providing access to that address. C. Incorrect: Network layer devices are responsible for end-to-end internetwork communications, and switches function at the data-link layer, which is concerned only with the local network. D. Incorrect: Application layer devices are concerned with specific services, not the general communications handled by switches.

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N10-002.01.06.002

Correct Answers: A and B A. Correct: Bridges connect segments at the data-link layer and propagate all broadcasts to both segments, which enables the two segments to function as a single LAN. B. Correct: Switches function at the data-link layer by forwarding packets based on their hardware addresses. Switches also forward broadcast messages to all of the connected computers, enabling them to function as a single LAN. C. Incorrect: Routers function at the network layer by stripping off the data-link layer header and reencapsulating the data for transmission over the other network. Routers do not forward broadcasts, which makes the segments they connect two separate LANs. D. Incorrect: Gateways operate at the application layer and do not physically connect cable segments like bridges, switches, and routers do, so they have no effect on the status of the LAN.

N10-002.01.06.003

Correct Answers: C A. Incorrect: Computers are digital and ISDN is a digital service, so no analog conversion is needed for computers connected by ISDN to communicate. B. Incorrect: A SAN is just a different type of LAN, which transmits data in digital form, so no analog conversion is necessary. C. Correct: Modems enable digital computers to communicate over analog telephone lines by converting the digital data to analog and back again. D. Incorrect: CSU/DSUs are used on leased telephone lines, which are usually digital, so there’s no need for a digital/analog conversion.

Objective 1.6

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N10-002.01.06.004

Correct Answers: B A. Incorrect: Replacing hubs with switches enhances a network’s performance by eliminating the shared network medium. This means that no MAC mechanism is needed, few collisions occur, and the bandwidth allotted to each computer is increased. B. Correct: Connecting computers with a hub creates a LAN, and routers are used to connect LANs. Connecting computers directly to routers makes no sense and will not result in a functioning network. C. Incorrect: Replacing bridges with routers creates an internetwork by dividing a single LAN into multiple LANs. This reduces the amount of broadcast traffic on each network, which can provide a noticeable increase in performance. D. Incorrect: Replacing routers with switches joins multiple separate networks into a single LAN without creating a shared network medium. The primary drawback of this arrangement is that all broadcast transmissions are now propagated throughout the entire network.


O B J E C T I V E

D O M A I N

2

Protocols and Standards

In order for computers to communicate over a network, they have to speak the same language. The languages that computers use for network communications are called protocols, and a familiarity with the many different protocols used during a typical network communications session is essential for a network administrator or a support technician. Computers use many different protocols simultaneously while communicating over a network, and to organize the functions of these protocols, network administrators use a theoretical construction called the Open Systems Interconnection (OSI) reference model. The OSI model divides the networking process into seven layers, with different protocols providing various functions at each layer. The networking protocols used today are mostly based on public standards developed and published by independent organizations, such as the Institute for Electrical and Electronics Engineers (IEEE) and the Internet Engineering Task Force (IETF). Open standards make it possible for networking hardware and software manufacturers to make products that can communicate with other manufacturers’ products.

Tested Skills and Suggested Practices The skills that you need to successfully master the Protocols and Standards objective domain on the Network+ Certification exam include:

Given an example, identifying a MAC address. Practice 1: Use the searchable database of organizationally unique identifiers (OUIs) provided by the IEEE at http://standards.ieee.org/regauth/oui/ index.shtml to look up the manufacturers of the network interface adapters your network uses.

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Practice 2: Compare the OUI information you find at the IEEE’sWeb site with the MAC addresses of your network interface adapters, as displayed in the Windows 2000 System Information console under the Components, Network, Adapter pane. Identifying the seven layers of the OSI model and their functions. Practice 1: Devise your own mnemonic based on the initials of the OSI model’s seven layers (such as “Please Do Not Throw Sausage Pizza Away”) to help you memorize them. Practice 2: Draw a diagram of the OSI reference model and list the most common protocols associated with each of the seven layers. Differentiating between the following network protocols in terms of routing, addressing schemes, interoperability, and naming conventions: TCP/IP, IPX/ SPX, NetBEUI, and AppleTalk. Practice 1: View the computers on the network using a workstation running each of the protocols listed and compare how the other network systems are identified. Practice 2: Study the standards and documentation for each of the specified protocols to learn how the computers on a network running each protocol communicate with each other. Identifying the OSI layers at which the following network components operate: hubs, switches, bridges, routers, and network interface cards. Practice 1: Study the documentation for an example of each of the product types listed and compare the information you find to the functions associated with each layer of the OSI reference model. Practice 2: Draw a diagram of your network and label the locations of the components listed previously. If your network does not include all of these components, expand the diagram to include a possible application for each type of device. Defining the purpose, function and/or use of the following protocols within TCP/IP: IP, TCP, UDP, FTP, TFTP, SMTP, HTTP, HTTPS, POP3/IMAP4, TELNET, ICMP, ARP, and NTP. Practice 1: Using the RFC index found at http://www.ietf.org/iesg/ 1rfc_index.txt, study the RFC documents for each of the protocols listed to learn about their basic functions.

Objective Domain 2

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Practice 2: Using a protocol analyzer, such as the Network Monitor application included with Windows 2000 Server, determine which of the protocols listed your network uses. Defining the function of TCP/UDP ports. Identifying well-known ports. Practice 1: Obtain a copy of the “Assigned Numbers” standard (RFC 1700) and locate the list of well-known ports in the document. See how many of the wellknown ports listed are associated with applications. Practice 2: Examine the configuration interface for a Web server, such as the Internet Information Server included with Windows 2000, and determine how to modify the port number a Web site uses. Then connect to the Web site using the alternative port number by specifying a socket in your Web browser. Identifying the purpose of the following network services (e.g., DHCP/BOOTP, DNS, NAT/ICS, WINS, and SNMP). Practice 1: Study the RFC documents for the services listed (where applicable) to determine the function of each one. Practice 2: Find out which of the services listed are being used on your network (if any) and what benefits they provide. Identifying IP addresses (IPv4, IPv6) and their default subnet masks. Practice 1: Convert some of the IP addresses your network uses to binary form, and using the values of the first four bits, determine what the default subnet mask for each address should be. Practice 2: Obtain a copy of RFC 2460, “Internet Protocol,Version 6 (IPv6) Specification,” and study the formation of IPv6 addresses. Identifying the purpose of subnetting and default gateways. Practice 1: Examine the TCP/IP client configuration parameters for a computer on your network to determine which default gateway address it uses. Locate the router with that address and identify the network to which it provides access. Practice 2: Create a list of the IP addresses and subnet masks you would use for the computers on a subnetted LAN with a Class B network address for which four bits have been borrowed to form the subnet addresses.

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Identifying the differences between public and private networks. Practice 1: Obtain a copy of RFC 1918, “Address Allocation for Private Internets,” and study how the IP address assignment for a private network differs from that of computers on the Internet. Practice 2: Examine the IP addresses your network’s computers use and determine if your network is public or private. Identifying the basic characteristics (e.g., speed, capacity, media) of the following WAN technologies: packet switching vs. circuit switching, ISDN, FDDI, ATM, Frame Relay, SONET/SDH, T1/E1, T3/E3, and OCx. Practice 1: Using the Web site or literature provided by your organization’s telephone service provider, determine which of the WAN technologies listed it can supply and how your organization might benefit from using them. Practice 2: Create a table listing the relative speeds and costs of the WAN technologies listed and determine which one provides the most bandwidth for the lowest cost. Defining the function of the following remote access protocols and services: RAS, PPP, PPTP, and ICA. Practice 1: Configure a modem-equipped computer to access a remote network, such as that of an ISP. Practice 2: Study the documentation for the operating systems your network uses to determine which of the protocols listed they support and how they use them. Identifying the following security protocols and describe their purpose and function: IPsec, L2TP, SSL, and Kerberos. Practice 1: Study the RFC documents for the protocols listed (where applicable) to determine the function of each one. Practice 2: Study the operating systems your network uses to determine which security protocols they support and how you can use them to provide extra protection for your network data.

Objective Domain 2

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Objective 2.1 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 1 in Chapter 5, “Data-Link Layer Protocols.” Institute of Electrical and Electronics Engineers. “Use of the IEEE assigned Organizationally Unique Identifier with ANSI/IEEE Std 802-1990 Local and Metropolitan Area Networks.” This document is available at the IEEE Web site at http://standards.ieee.org/regauth/oui/tutorials/lanman.html.

Objective 2.2 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 2 in Chapter 1, “Networking Basics.” Microsoft Corporation. Windows 2000 Server Resource Kit. Volume: TCP/IP Core Networking Guide. Redmond, Washington: Microsoft Press, 2000. Review Appendix A, “OSI Model.”

Objective 2.3 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lessons 1, 2, and 3 in Chapter 6, “Network Layer Protocols.” Microsoft Corporation. Windows 2000 Server Resource Kit. Volume: TCP/IP Core Networking Guide. Redmond, Washington: Microsoft Press, 2000. Review Appendix B, “Windows 2000 Network Architecture.”

Objective 2.4 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 2 in Chapter 1, “Networking Basic;” Lessons 2 and 3 in Chapter 2, “Network Hardware;” and Lessons 1, 2, and 3 in Chapter 3, “Network Connections.” Microsoft Corporation. Windows 2000 Server Resource Kit. Volume: TCP/IP Core Networking Guide. Redmond, Washington: Microsoft Press, 2000. Review Appendix A, “OSI Model.”

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Objective 2.5 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 1 in Chapter 8, “TCP/IP Fundamentals.” Internet Engineering Task Force. RFC 791: “Internet Protocol.” This document is in the public domain and is available as a free download at http://www.rfc-editor.org/rfc.html. Internet Engineering Task Force. RFC 793: “Transmission Control Protocol.” This document is in the public domain and is available as a free download at http:// www.rfc-editor.org/rfc.html. Internet Engineering Task Force. RFC 768: “User Datagram Protocol.” This document is in the public domain and is available as a free download at http://www.rfc-editor.org/ rfc.html. Internet Engineering Task Force. RFC 959: “File Transfer Protocol.” This document is in the public domain and is available as a free download at http://www.rfc-editor.org/ rfc.html. Internet Engineering Task Force. RFC 783: “TFTP Protocol (revision 2).” This document is in the public domain and is available as a free download at http://www.rfceditor.org/rfc.html. Internet Engineering Task Force. RFC 2821: “Simple Mail Transfer Protocol.” This document is in the public domain and is available as a free download at http://www. rfc-editor.org/rfc.html. Internet Engineering Task Force. RFC 2616: “Hypertext Transfer Protocol—HTTP/1.1.” This document is in the public domain and is available as a free download at http://www.rfc-editor.org/rfc.html. Internet Engineering Task Force. RFC 1939: “Post Office Protocol—Version 3.” This document is in the public domain and is available as a free download at http://www.rfceditor.org/rfc.html. Internet Engineering Task Force. RFC 2060: “Internet Message Access Protocol—Version 4, rev 1.” This document is in the public domain and is available as a free download at http://www.rfc-editor.org/rfc.html. Internet Engineering Task Force. RFC 854: “Telnet Protocol Specification.” This document is in the public domain and is available as a free download at http://www.rfceditor.org/rfc.html. Internet Engineering Task Force. RFC 792: “Internet Control Message Protocol.” This document is in the public domain and is available as a free download at http://www. rfc-editor.org/rfc.html.

Objective Domain 2

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Internet Engineering Task Force. RFC 826: “Ethernet Address Resolution Protocol: Or converting network protocol addresses to 48.bit Ethernet address for transmission on Ethernet hardware.” This document is in the public domain and is available as a free download at http://www.rfc-editor.org/rfc.html. Internet Engineering Task Force. RFC 1034: “Domain Names—Concepts and Facilities” and RFC 1035: “Domain Names—Implementation and Specification.” These documents are in the public domain and are available as a free download at http://www. rfc-editor.org/rfc.html.

Objective 2.6 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 1 in Chapter 7, “Transport Layer Protocols.” Internet Engineering Task Force. RFC 1700: “Assigned Numbers.” This document is in the public domain and is available as a free download at http://www.rfc-editor.org/ rfc.html.

Objective 2.7 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 1 in Chapter 10, “TCP/IP Applications” and Lesson 3 in Chapter 13, “Network Security.” Internet Engineering Task Force. RFC 2131: “Dynamic Host Configuration Protocol.” This document is in the public domain and is available as a free download at http:// www.rfc-editor.org/rfc.html. Internet Engineering Task Force. RFC 1001: “Protocol Standard for a NetBIOS Service on a TCP/UDP Transport: Concepts and Methods” and RFC 1002: “Protocol Standard for a NetBIOS Service on a TCP/UDP Transport: Detailed Specifications.” These documents are in the public domain and are available as a free download at http://www. rfc-editor.org/rfc.html. Internet Engineering Task Force. RFC 1034: “Domain Names—Concepts and Facilities” and RFC 1035: “Domain Names—Implementation and Specification.” These documents are in the public domain and are available as a free download at http://www. rfc-editor.org/rfc.html. Internet Engineering Task Force. RFC 1157: “Simple Network Management Protocol (SNMP).” This document is in the public domain and is available as a free download at http://www.rfc-editor.org/rfc.html.

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Objective 2.8 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 2 in Chapter 8, “TCP/IP Fundamentals.” Internet Engineering Task Force. RFC 2460: “Internet Protocol, Version 6 (IPv6) Specification.” This document is in the public domain and is available as a free download at http://www.rfc-editor.org/rfc.html.

Objective 2.9 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 2 in Chapter 8, “TCP/IP Fundamentals” and Lesson 2 in Chapter 11, “TCP/IP Configuration.” Microsoft Corporation. Windows 2000 Server Resource Kit. Volume: TCP/IP Core Networking Guide. Redmond, Washington: Microsoft Press, 2000. Review Chapter 1, “Introduction to TCP/IP.”

Objective 2.10 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 2 in Chapter 8, “TCP/IP Fundamentals.” Internet Engineering Task Force. RFC 1918: “Address Allocation for Private Internets.” This document is in the public domain and is available as a free download at http:// www.rfc-editor.org/rfc.html.

Objective 2.11 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 3 in Chapter 12, “Remote Network Access.” Microsoft Corporation. Windows 2000 Server Resource Kit. Volume: Internetworking Guide. Redmond, Washington: Microsoft Press, 2000. Review Chapter 7, “Remote Access Server.”

Objective Domain 2

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Objective 2.12 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lessons 1 and 2 in Chapter 12, “Remote Network Access.” Internet Engineering Task Force. RFC 1661: “The Point-to-Point Protocol (PPP).” This document is in the public domain and is available as a free download at http://www.rfceditor.org/rfc.html.

Objective 2.13 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 4 in Chapter 13, “Network Security.” Microsoft Corporation. Internet Information Server Resource Kit. Volume: Internet Information Server 5.0 Resource Guide. Redmond, Washington: Microsoft Press, 2000. Review Chapter 9, “Security.” Internet Engineering Task Force. RFC 2411: “IP Security Document Roadmap.” This document is in the public domain and is available as a free download at http://www.rfceditor.org/rfc.html.


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O B J E C T I V E

2 . 1

Given an example, identify a MAC address.

The protocols operating at the data-link layer of the OSI reference model are responsible for the communication between computers on a local area network (LAN). For this communication to take place, every device on a LAN must have a unique identifier, which is called a media access control (MAC) address or hardware address. The header that the data-link layer protocol adds to every packet transmitted over the network contains two 6-byte fields that contain the addresses of the sending and receiving computers. When a computer transmits a packet, the network adapters in all of the other computers on the LAN read the destination address from the data-link layer protocol header to determine if that packet is addressed to them. If it is, the adapter passes the packet to the computer for processing; if it isn’t, the adapter discards the packet. It’s important to understand that protocols operating at other layers of the OSI model may have their own addressing systems, which are completely independent of the MAC address. The Internet Protocol (IP), for example, operates at the network layer and has its own separate 32-bit address space. A computer running Ethernet at the datalink layer and IP at the network layer has two different and independent addresses. The format and method for assigning MAC addresses can differ from protocol to protocol, but most of the data-link layer protocols in use (such as Ethernet and Token Ring) have MAC addresses permanently assigned to the network interface adapter by its manufacturer. These MAC addresses are six bytes long and are typically expressed as six hexadecimal values separated by colons (such as 00:D0:B7:AD:1A:7B). The first three bytes of a MAC address consist of a value called an organizationally unique identifier (OUI), which the IEEE assigns to the network adapter manufacturer. When the manufacturer builds its network adapters, it hardcodes each unit with a MAC address that consists of the manufacturer’s assigned 3-byte OUI plus a 3-byte value that uniquely identifies that particular adapter. This two-tiered address assignment system prevents any possibility of two adapters having the same MAC address. In addition to the unique MAC addresses assigned to network interface adapters, there are also specific MAC addresses that are reserved for special uses, such as the address FF:FF:FF:FF:FF:FF, which is used as a broadcast address. When a computer transmits a packet on the LAN with a broadcast address as its destination, every other computer on the network reads and processes the packet.

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Objective 2.1 Questions N10-002.02.01.001 Which of the following values would be a valid MAC address for a network interface adapter? A. 01:AE:27:1H:4B:21 B. FF:FF:FF:FF:FF:FF C. 192.168.6.32 D. 00:1A:6B:31:9A:4E

N10-002.02.01.002 What is the 3-byte value called that the IEEE assigns to each manufacturer of network interface adapters, which it must use as the first three bytes of its MAC addresses? A. A hardware address B. An OUI C. A broadcast address D. An IEEE address

N10-002.02.01.003 Protocols operating at which layers of the OSI model can use MAC addresses to address their packets? (Choose two.) A. Physical B. Data-link C. Network D. Transport

Objective 2.1

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N10-002.02.01.004 Which of the following protocols have MAC addresses in their headers? (Choose three.) A. Ethernet B. IP C. IPX D. Token Ring


Correct Answers: D A. Incorrect: Although the format of the value is correct for a MAC address, the individual byte values are expressed in hexadecimal form, and 1H is not a valid hexadecimal number. Hexadecimal numbers can use only the characters 0 through 9 and A through F. B. Incorrect: Although this is a valid MAC address, it would never be assigned to a network interface adapter because it is reserved for use as a broadcast address. C. Incorrect: This value could not be a MAC address because it consists only of decimal values. This is actually a 32-bit IP address. D. Correct: A MAC address assigned to a network interface adapter consists of six 1-byte hexadecimal values separated by colons.

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N10-002.02.01.002

Correct Answers: B A. Incorrect: The term hardware address is synonymous with MAC address and refers to the entire 6byte address assigned to a network interface adapter, not just the 3-byte value the IEEE assigns. B. Correct: The IEEE assigns a unique OUI to each adapter manufacturer to ensure that no two products made by different manufacturers can possibly have the same MAC address. C. Incorrect: A broadcast address is a special 6-byte MAC address that systems use to transmit a packet to all of the computers on a LAN. The IEEE does not assign it to any particular manufacturer. D. Incorrect: Although the IEEE does assign 3-byte values to network interface adapter manufacturers, these values are not called IEEE addresses.

N10-002.02.01.003

Correct Answers: B and C A. Incorrect: The physical layer is concerned with raw signals, such as electrical charges, and knows nothing about addresses of any kind. B. Correct: The data-link layer protocol uses MAC addresses to send its packets to other computers on the same LAN. C. Correct: IP (at the network layer) uses its own address space to identify the computers on the network; it does not use MAC addresses. However, Novell’s Internetwork Packet Exchange (IPX) protocol does use MAC addresses to identify computers at the network layer. D. Incorrect: All packet addressing is performed at the data-link and network layers. The transport layer protocol headers contain port numbers, but not MAC addresses.

N10-002.02.01.004

Correct Answers: A, C, and D A. Correct: Ethernet is a data-link layer protocol that uses MAC addresses in its header to identify the packet’s source and destination computers. B. Incorrect: IP is a network layer protocol that does not use MAC addresses in its header fields. C. Correct: IPX is a network layer protocol that uses MAC addresses to identify specific computers on a network. D. Correct: Token Ring is a data-link layer protocol that uses MAC addresses in its header to identify the packet’s source and destination computers.

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O B J E C T I V E

2 . 2

Identify the seven layers of the OSI model and their functions.

The OSI reference model is a tool developed to organize the many different functions involved in data networking into a regulated seven layer hierarchy that technicians and developers can use to describe and reference specific network activities. Originally intended as the model for a networking protocol stack that never materialized commercially, the OSI model is now used only as a teaching and reference tool. Networking practitioners and reference materials frequently refer to protocols as operating at a specific layer of the OSI model, and an understanding of these layers and their functions is essential for anyone preparing to take the Network+ Certification exam or to work as a network administrator. The OSI reference model was not designed with any existing protocol stack in mind, nor were any of the protocol stacks used today designed to conform exactly to the model’s layers. Many protocols have functions that encompass more than one layer despite being referenced as operating at one particular layer. The OSI model is an abstract representation of a computer’s protocol stack, which is responsible for taking the information an application or service generates and packaging it for transmission over a network. The protocols operating at the various layers receive data from the layer above it, package it by adding a protocol header (and in one case, a footer), and pass it to the layer below. By the time the data reaches the bottom layer of the model (and the bottom of the protocol stack), it is ready for transmission. This process is called data encapsulation. When the data arrives at its destination system, it travels up through the protocol stack and the protocols operating at the various OSI model layers perform the same functions in reverse until the data reaches the destination application or service. For two computers to communicate on a network, they must be running the same protocols at each layer of the OSI model. For example, you might have two computers that are both running Ethernet at the data-link layer, but if at the network layer one is running IP and the other IPX, no useful communication can take place.

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Readiness Review—Exam N10-002 The seven layers of the OSI reference model and their functions are (from top to bottom):

Application—The protocols operating at the application layer provide services directly to the applications running on the computer. Application layer protocols are the entrance points to the protocol stack that programs use when they require network communications. Some of the protocols operating at the application layer are Hypertext Transfer Protocol (HTTP), Simple Mail Transfer Protocol (SMTP), and File Transfer Protocol (FTP). Presentation—The presentation layer is responsible for translating between the syntaxes different systems use, enabling computers of completely different types to communicate. Before transmitting its data, the sending computer converts its native syntax, called an abstract syntax, to a transfer syntax that is common to both computers. The receiving computer then converts the transfer syntax to its own abstract syntax, which may be different from the sender’s. There are no separate presentation layer protocols; this layer’s functions are incorporated into protocols running at other layers. Session—The session layer provides a variety of services that regulate the communication (called a dialog) between two computers. Two of these services are dialog control, which involves the selection of a communications mode that specifies whether the computers can send messages alternately or simultaneously (one-way or two-way communications), and dialog separation, which is the creation of checkpoints in the data stream so two communicating computers can synchronize their actions. Transport—The protocols operating at the transport layer provide complementary communication services to the network layer protocol, such as flow control (the dynamic regulation of transmission speed), guaranteed delivery (the acknowledgment of successfully transmitted messages), and error detection (the use of checksums to verify that data has been transmitted without error). Protocol suites typically have at least two protocols operating at the transport layer: one that provides connection-oriented service and one that provides connectionless service. For example, the transport layer protocols in the TCP/IP (Transmission Control Protocol/Internet Protocol) suite are the Transmission Control Protocol (TCP), which is connection-oriented, and the User Datagram Protocol (UDP), which is connectionless.

Objective 2.2

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Network—The network layer protocol is the primary end-to-end transport service on an internetwork. Although data-link layer protocols are used only for communications between computers on the same LAN, network layer protocols are responsible for the complete transmission of data from a computer on one network to a computer on another. Some of the functions the network layer protocol provides are addressing (the identification of the message’s ultimate recipient), routing (the direction of data packets through an internetwork to their destinations), and fragmentation (the splitting of data packets into smaller pieces to accommodate the limitations of interim networks on the transmission path). The most popular network layer protocols are IP, IPX, and NetBIOS Extended User Interface (NetBEUI). Data-link—The data-link layer protocol is responsible for the final packaging of the data before it is transmitted over the network. On a LAN, the data-link layer protocol consists of a frame format, which is the configuration of the header and footer used to encapsulate the network layer data; a MAC mechanism, which is a method for providing the computers on a LAN with equal opportunities to transmit their data over the shared network medium; and one or more physical layer implementations, which specify the types of cable or other media used to construct the network and the configuration of the network installation. Unlike the upper layer protocols, which are software only, a data-link layer LAN protocol is typically implemented as a network interface adapter and its accompanying device driver. The most common data-link layer LAN protocols are Ethernet and Token Ring. Physical—The physical layer specifies the type of cable or other technology used to create the network medium, how the technology should be installed, and how the data should be encoded into signals for transmission over that medium. The physical layer deals with raw signals only, such as electrical charges and pulses of light; it cannot interpret those signals as data or perceive their higher functions.

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Objective 2.2 Questions N10-002.02.02.001 Which layer of the OSI reference model is primarily responsible for getting data to its ultimate destination on an internetwork? A. Data-link B. Network C. Transport D. Application

N10-002.02.02.002 At which layer does the UDP operate? A. Data-link B. Network C. Transport D. Application

N10-002.02.02.003 At which layer of the OSI reference model are the protocols responsible for controlling access to the network medium? A. Physical B. Data-link C. Network D. Transport

Objective 2.2

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Correct Answers: B A. Incorrect: Data-link layer protocols are concerned only with transmissions between computers on the same LAN. The destination address in a data-link layer protocol header always identifies a system on the same LAN as the transmitter. Data-link layer protocols have no knowledge of other networks and therefore cannot be responsible for internetwork communications. B. Correct: The network layer is the first layer (working up from the bottom of the model) that is concerned with delivering data packets to their final destinations. The destination address in a network layer protocol header identifies the final recipient of the packet and never changes. C. Incorrect: Transport layer protocols do provide end-to-end services, but since transport layer data is carried inside network layer datagrams, the network layer protocol holds the primary responsibility for internetwork communications. D. Incorrect: The application layer protocol is concerned only with providing a service to an application running on the computer. Although application layer protocols use the end-to-end communication services the network and transport layers provide, they are not directly involved in the internetwork communications process.

N10-002.02.02.002

Correct Answers: C A. Incorrect: The protocols operating at the data-link layer on a LAN are typically those associated with specific hardware products, such as Ethernet and Token Ring. There is no UDP hardware. B. Incorrect: A protocol suite typically has only a single protocol carrying application data at the network layer. IP is the network layer protocol in the TCP/IP suite, so UDP can’t function there too. C. Correct: UDP is a protocol that operates at the transport layer and is the connectionless counterpart to TCP. D. Incorrect: Application layer protocols provide services directly to applications and do not participate in the transport of data across a network.

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N10-002.02.02.003

Correct Answers: B A. Incorrect: Although the physical layer is responsible for the configuration of the network medium and the type of signaling used to transmit data over it, it has no concept of the network as a data transfer medium and does not participate in the MAC process. B. Correct: The data-link layer protocols used on LANs, such as Ethernet and Token Ring, call for a shared network medium, and a MAC mechanism is an essential component of the protocol. Without the MAC mechanism, one computer could monopolize the network for a long time, or two computers could transmit at the same time, corrupting both their data. C. Incorrect: The network layer protocol is responsible for end-to-end internetwork communication, which transcends the mechanisms involving a single network medium. Data packets traveling to a distant location may pass through many different networks on their journey, requiring different MAC mechanisms. D. Incorrect: As in the network layer, the protocols operating at the transport layer are not involved in the mechanisms a specific network medium uses.

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O B J E C T I V E

2 . 3

Differentiate between the following network protocols in terms of routing, addressing schemes, interoperability, and naming conventions: TCP/IP, IPX/SPX, NetBEUI, AppleTalk.

The protocols at the network and transport layers of the OSI reference model generally do not operate independently. Instead, the protocols are grouped into units called protocol suites or protocol stacks that provide complementary services to each other. These suites typically contain many different protocols that operate at various layers of the OSI model, but they are usually installed as a single unit. The protocol suites used by operating systems today are designed for networks of different sizes and configurations and often to support different types of computers. In many cases, it’s possible to install more than one protocol suite on a computer, providing access to resources accessible with each separate set of protocols.

TCP/IP—The TCP/IP suite is the most commonly used protocol stack in the networking industry. Named for the suite’s network layer protocol (IP) and its connection-oriented transport layer protocol (TCP), UNIX and Windows computers use TCP/IP as their default protocols, and the suite is also the common language of the Internet. TCP/IP has its own self-contained addressing system, which is one of its greatest strengths. Every computer on a network must have its own unique IP address to be identified by the other computers. The IP address contains a network identifier, which specifies the network on which the computer is located, and a host identifier, which is a unique value for the network interface in that particular computer. Because the protocols were designed for the Internet, TCP/IP’s routing capabilities are almost infinitely expandable. Internet computers frequently route packets through dozens of networks on the way to their destinations by using dynamic routing protocols that enable routers to share information with each other and compensate automatically for changes in the network infrastructure. The

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Readiness Review—Exam N10-002 TCP/IP protocols were designed to be platform-independent, which is one of the reasons for the self-contained IP addressing system. Virtually every operating system and computing platform in use supports TCP/IP, enabling computers of all different types to communicate with each other. Although TCP/IP relies primarily on IP addresses to move data from one computer to another, the protocols also support the use of human-friendly names using the Domain Name System (DNS).

IPX/SPX—The Internetwork Packet Exchange/Sequenced Packet Exchange (IPX/SPX) protocol suite is a Novell, Inc., product that is intended for use with its NetWare operating system. The suite is named for the IPX protocol, which is the suite’s network layer protocol, and SPX, which provides connection-oriented service at the transport layer. Like TCP/IP, IPX/SPX consists of many different protocols, but IPX/SPX is intended for use on LANs only. It would not be a suitable protocol suite for the Internet. IPX/SPX uses separate identifiers for networks and the nodes on the networks like TCP/IP, but the addressing system is not platformindependent or self-contained. Network administrators or the operating system assign network addresses during the Novell NetWare installation, but for node addresses, IPX/SPX relies on the MAC addresses coded into the computers’ network interface adapters. This arrangement is suitable for LANs running common data-link layer protocols, such as Ethernet and Token Ring, but IPX/SPX does not provide the same cross-platform interoperability as TCP/IP. Although there are other operating systems that can run IPX/SPX (Windows has its own IPX-compatible protocol called NWLink, for example), this capability is used primarily to provide other systems with NetWare connectivity. Networks not running NetWare servers rarely, if ever, use IPX/SPX. IPX/SPX is routable and can use dynamic routing protocols like TCP/IP, but because the suite is intended for use on private internetworks only, routes are limited to 16 hops. IPX/SPX does not have its own name space, and since NetWare is a client/server operating system only, only servers are assigned names. NetBEUI—NetBEUI is a protocol that is used almost exclusively on small Windows LANs. NetBEUI was the default protocols stack in the first versions of Windows that included network clients, but it was soon replaced by TCP/IP as the default. NetBEUI does not use addresses of any kind to identify the computers on a network; instead, it uses NetBIOS names, which on Windows computers are 15 characters long. NetBEUI also lacks any type of network identifier, resulting in a protocol that is not routable and is therefore suitable for only small, single-segment LANs. Because of its limited utility, NetBEUI is not interoperable with other computing platforms. It does, however, provide a simple networking protocol stack for small LANs that require no manual tuning or configuration whatsoever.

Objective 2.3

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AppleTalk—AppleTalk is a protocol suite developed for Macintosh computers, which have been equipped with integrated networking hardware and software virtually since their inception. Like NetBEUI, AppleTalk was designed to provide basic networking capabilities for relatively small networks. Although it doesn’t excel in performance, AppleTalk does have more capabilities than NetBEUI. AppleTalk is routable, and it has a hierarchical addressing system that automatically assigns a node ID to each computer and a network number to each network. AppleTalk computers also have friendly names that are gathered into groups called zones, which makes it easier for a user to locate a particular computer.To provide Macintosh connectivity, there are several other computing platforms that provide AppleTalk interoperability (such as NetWare and Windows), although an additional software product is sometimes required. Like NetBEUI, AppleTalk has been largely phased out in favor of TCP/IP, which provides the Internet access and other features that AppleTalk lacks.

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Objective 2.3 Questions N10-002.02.03.001 Which of the following protocol suites provide their own self-contained addresses for each computer on the network? (Choose two.) A. TCP/IP B. IPX/SPX C. NetBEUI D. AppleTalk

N10-002.02.03.002 Which of the following protocol suites supports Internet routing? A. TCP/IP B. IPX/SPX C. NetBEUI D. AppleTalk

N10-002.02.03.003 Which of the following protocol suites is not associated with a particular operating system? A. TCP/IP B. IPX/SPX C. NetBEUI D. AppleTalk

Objective 2.3


Correct Answers: A and D A. Correct: The IP has its own 32-bit address space that contains both a network identifier and a host identifier, the latter of which refers to a specific computer on the network. B. Incorrect: The IPX/SPX protocol suite does use addresses to identify the computers on a network, but protocols do not supply the addresses. Instead, IPX/SPX uses the hardware addresses that manufacturers assign to network interface adapters. C. Incorrect: NetBEUI does not use any form of address to identify the computers on a network. NetBEUI uses NetBIOS names instead. D. Correct: AppleTalk has its own self-contained address space that uses 8-bit node IDs to identify each computer and 16-bit network numbers.

N10-002.02.03.002

Correct Answers: A A. Correct: TCP/IP is the only protocol suite used on the Internet, and it includes highly-scalable routing capabilities using dynamic routing protocols, such as Routing Information Protocol (RIP) and Open Shortest Path First (OSPF). Internet routing is made possible by the registration of network addresses with an organization called the Internet Assigned Numbers Authority (IANA). This registration prevents Internet network addresses from being duplicated. B. Incorrect: IPX/SPX is routable, but can be used only on LANs because it has no facility for registering its network addresses; it is therefore not capable of Internet routing. C. Incorrect: NetBEUI uses no network identifiers, and therefore has no means of routing packets to other networks. D. Incorrect: AppleTalk is a routable protocol, but it has no means of registering its network addresses, so it is incapable of Internet routing.

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68


N10-002.02.03.003

Correct Answers: A A. Correct: Developed for use on the fledgling Internet, the TCP/IP protocols were designed to support a variety of computing platforms and operating systems. B. Incorrect: Novell developed the IPX/SPX protocol suite specifically for its NetWare operating system, and it is used virtually exclusively for NetWare connectivity. C. Incorrect: Although it has been used by other operating systems, NetBEUI is associated primarily with Microsoft Windows. D. Incorrect: AppleTalk was designed for Macintosh computers, and other operating systems use it only to provide network connectivity to Macintoshes.

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O B J E C T I V E

2 . 4

Identify the OSI layers at which the following network components operate: hubs, switches, bridges, routers, network interface cards.

Networks are usually held together by cables, but there are many other hardware components operating at various layers of the OSI reference model that are used to build networks. Some of these components are:

Hubs—A hub is a wiring nexus used to connect all of the computers and other network devices on a network using a star topology. The hub’s functionality depends on the data-link layer protocol the network is using. On an Ethernet network, the hub is a simple, physical-layer device sometimes called a multiport repeater that takes the signals arriving through any one of its ports, amplifies them, and forwards them out through all of the other ports. This creates a shared network medium. Because Ethernet hubs operate at the physical layer, they are concerned with only the signals traveling over the network, not with data structures, addresses, or any other upper layer concepts. On a Token Ring network, the hub is called a multistation access unit (MAU) and has considerably more capability than an Ethernet hub. Token Ring uses a ring topology for its communications, but because the network is physically cabled using a star (just like Ethernet), the ring is implemented logically, inside the hub. A Token Ring MAU has to initialize each connected computer by adding it to the ring and forwarding incoming data packets out through the other ports one at a time instead of simultaneously. This requires the MAU to function as much at the data-link layer as at the physical layer. Switches—A switch is a data-link layer device that looks much like an Ethernet hub, except that instead of forwarding incoming packets out through all of its ports, it reads the destination address in each packet and forwards it out through only the port to which the destination system is connected. This essentially provides each pair of computers on the network with a dedicated connection using the full bandwidth of the medium. Since other computers are not contending for use of the same bandwidth (except in the case of broadcast transmissions), there are few, if any,

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Readiness Review—Exam N10-002 collisions, and the overall efficiency of the network increases drastically. Many networks use switches instead of routers to connect their cable segments. Replacing routers with switches turns an internetwork into what is essentially one large LAN, but since the bandwidth isn’t shared, there is no performance degradation.

Bridges—A bridge is a data-link layer device that splits a network into two separate collision domains and reduces traffic levels by filtering data packets. The bridge compiles a list of the addresses for the devices on each side of the network. When a packet arrives at the bridge, it reads the destination address from the datalink layer protocol header. If the packet is a broadcast or is destined for a computer on the other side of the network, the bridge forwards it out to the other segment. If the packet is destined for a computer located on the same segment as the sender, the bridge discards it because there is no need to forward it to the other segment. This action provides a significant reduction in overall network traffic. Routers—A router is a network layer device that connects two or more LANs to form an internetwork. Like a bridge, a router forwards packets based on their destination addresses, but in this case, the address the router uses for each packet is found in the network layer protocol header, which specifies the ultimate destination of the packet. On a simple internetwork consisting of two LANs, the router works like a bridge, forwarding only the packets addressed to the other network. On more complex internetworks, however, routers make decisions regarding the best route that a packet should take to its final destination. Routers on large internetworks communicate with each other using specialized routing protocols to exchange information about the network’s configuration. These protocols enable the routers to alter their procedures as network conditions change. Network interface cards (NICs)—A network interface card (or more precisely, a network interface adapter, since the device does not always take the form of a separate card) is a device that operates at both the physical and the data-link layers. At the physical layer, the NIC plugs into an expansion slot in a computer and provides the interface between the computer and the network medium, typically as a cable port. At the data-link layer, the NIC (along with the network adapter driver) implements the data-link layer protocol functions, such as the MAC mechanism, as well as physical layer functions, such as signal encoding.

Objective 2.4

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Objective 2.4 Questions N10-002.02.04.001 Which of the following devices do not operate at the data-link layer of the OSI reference model? (Choose two.) A. An Ethernet hub B. A bridge C. A switch D. A router

N10-002.02.04.002 Which of the following devices eliminates all unicast collisions from a network? A. An Ethernet hub B. A bridge C. A switch D. A router

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Correct Answers: A and D A. Correct: Although it is associated with Ethernet, a data-link layer protocol, an Ethernet hub is strictly a physical layer device. Its primary functions are amplifying and propagating physical layer signals, such as electrical changes and pulses of light (depending on the nature of the network medium). B. Incorrect: A bridge is strictly a data-link layer device because it filters packets based on the addresses found in the data-link layer protocol header. C. Incorrect: A switch is a data-link layer device because it relies on the addresses in the data-link layer protocol header to forward its packets out through the correct port. D. Correct: Routers forward packets based on the addresses in the network layer protocol header, which makes them network layer devices. While processing a packet, a router strips off its data-link layer protocol header and generates a new one later. This enables a router to connect networks that are running different protocols at the data-link layer.

N10-002.02.04.002

Correct Answers: C A. Incorrect: Ethernet hubs simply forward packets generated by one computer to all of the other computers on the network simultaneously. If two computers transmit data at precisely the same time, a collision will occur despite the presence of a hub. B. Incorrect: Bridges propagate packets between two network segments based on their destination addresses. By filtering out packets that are not destined for the other segment, bridges reduce network traffic and the number of collisions, but they do not eliminate them completely. Two computers on the same side of a bridge that transmit simultaneously will still generate a collision. C. Correct: Switches are essentially “intelligent” hubs that forward incoming packets to their destination systems only. This forms a dedicated connection between the two computers involved in a unicast transmission, which eliminates the possibility of a collision. Collisions can still occur when broadcast transmissions are involved, but not during unicasts. D. Incorrect: Routers operate at the network layer of the OSI model and are not involved in detecting or preventing collisions, which are data-link layer processes.

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O B J E C T I V E

2 . 5

Define the purpose, function and/or use of the following protocols within TCP/IP: IP, TCP, UDP, FTP, TFTP, SMTP, HTTP, HTTPS, POP3/ IMAP4, TELNET, ICMP, ARP, NTP.

The TCP/IP suite consists of many different protocols, all of which work together to provide efficient communications. Some of these protocols are:

Internet Protocol (IP)—IP is the network layer protocol that is primarily responsible for end-to-end internetwork communications. Some of the functions of IP are addressing (identifying the source and destination of each packet), fragmentation (splitting packets into smaller units to transmit them over networks that don’t support larger packets), and routing (directing packets to their destinations using the most efficient path through the internetwork). Transmission Control Protocol (TCP)—TCP is a transport layer protocol that provides a connection-oriented service with features such as guaranteed delivery, packet acknowledgment, error detection, and flow control. TCP generates a large amount of network traffic overhead and is used for applications that must transmit large amounts of data with complete accuracy and reliability. User Datagram Protocol (UDP)—UDP is a transport layer protocol providing a connectionless service that generates little overhead but sacrifices the extensive array of services TCP provides. UDP is typically used for transmitting amounts of data small enough to fit into a single packet in a request and response format that functions as a tacit acknowledgment. File Transfer Protocol (FTP)—FTP is an application layer protocol that makes it possible for a TCP/IP computer to perform basic file management tasks on another computer as well as to upload and download files. In some cases, the FTP protocol is an application unto itself, while in others its functions are integrated into another application. FTP uses the TCP protocol for its transport services.

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Trivial File Transfer Protocol (TFTP)—TFTP is a simplified version of FTP that uses UDP at the transport layer and transfers files without the file management interface FTP supplies. TFTP was developed for diskless workstations that had to download an executable operating system file from a server during the system boot process, and it is rarely used today. Simple Mail Transfer Protocol (SMTP)—SMTP is the application layer protocol responsible for carrying e-mail messages from clients to servers and between servers. Hypertext Transfer Protocol (HTTP)—HTTP is the application layer protocol Web browser clients use to request and receive files from Web servers. Secure Hypertext Transfer Protocol (HTTPS or S-HTTP)—HTTPS is a secured version of the HTTP protocol that enablesWeb clients and servers to transmit data in encrypted form. Post Office Protocol, version 3 (POP3)—POP3 is an application layer protocol that provides mailbox services for e-mail clients. SMTP transmits e-mail destined for a particular client to the POP3 server, where it waits for the client to connect to it and download the messages. Internet Message Access Protocol, version 4 (IMAP4)—IMAP4 is another mailbox protocol that operates at the application layer. It provides a greater array of services than POP3. IMAP users can store their mail messages on the server permanently, organize them by creating folders, search for e-mail messages stored on the server based on their contents, and select individual messages for download. Telecommunication Network Protocol (Telnet)—Telnet is an application layer protocol that enables a user to log on remotely to a computer on the network and execute commands there. Telnet is therefore essentially a remote control command line application. The value of Telnet is limited by the functionality of the command line on the computers involved. On UNIX systems, which are command line-based, for example, Telnet is a powerful tool. On Windows, which has relatively limited command line capabilities, Telnet’s functionality is limited.

Objective 2.5

75

Internet Control Message Protocol (ICMP)—ICMP is a network layer protocol that TCP/IP computers use to transmit specialized diagnostic and error messages. The Ping utility, for example, uses ICMP Echo Request and Echo Reply messages to test whether another TCP/IP computer on the network is functioning. Routers send ICMP messages to transmitting computers when they are unable to forward their messages to the specified destination. Address Resolution Protocol (ARP)—ARP is a protocol (whether it runs at the data-link or the network layer is debatable) that IP uses to determine the hardware address of a computer on the LAN based on its IP address. When a TCP/IP computer has a packet to send to a particular IP address, it transmits an ARP request message containing the address as a broadcast. The computer using that address must respond by sending its hardware address in a reply message. The computer then feeds the hardware address to the data-link layer protocol, which uses it to transmit the packet to the destination. Network Time Protocol (NTP)—NTP is an application layer protocol that TCP/IP computers use to send time signals to each other, enabling them to synchronize their clocks.

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Objective 2.5 Questions N10-002.02.05.001 Which of the following protocols provides connectionless service at the transport layer of the OSI reference model? A. UDP B. TCP C. IP D. ARP

N10-002.02.05.002 A network administrator is installing an e-mail system and needs to provide a mailbox service for the network users. Which of the following protocols can provide this service? (Choose two.) A. SMTP B. HTTP C. POP3 D. IMAP4

N10-002.02.05.003 Which of the following conditions most profoundly limits the functionality of a Telnet session connecting one computer to another? A. The use of a slow dial-up connection between the two computers B. The use of UDP instead of TCP at the transport layer C. The use of different operating system versions on the two computers D. Limited command line capabilities on the remote computer

Objective 2.5

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N10-002.02.05.004 Which of the following protocols does not operate at the application layer of the OSI model? A. ICMP B. Telnet C. NTP D. FTP

N10-002.02.05.005 Which of the following protocols do Web browsers use to communicate with Web servers? A. TFTP B. NTP C. SMTP D. HTTP


Correct Answers: A A. Correct: UDP is the simpler of the two TCP/IP transport layer protocols. Its header is only eight bytes, compared to the 20-byte header TCP/IP uses. UDP also uses no messages other than those carrying application data to and from the destination. Because UDP does not use control messages to establish a connection before sending the application data, it is called a connectionless protocol. B. Incorrect: TCP uses a procedure called a three-way handshake to establish a connection with the destination computer before it begins transmitting application data, which is why it is called a connection-oriented protocol. C. Incorrect: IP is a connectionless protocol, but it operates at the network layer, not the transport layer. D. Incorrect: ARP relies on broadcast messages to perform its function because the transmitting computer does not have sufficient information about the intended destination to address unicasts messages to it. Unicasts are required for connection-oriented service, so ARP is technically considered connectionless. However, although it’s feasible to argue that ARP operates at either the data-link or the network layer, it definitely doesn’t operate at the transport layer.

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N10-002.02.05.002

Correct Answers: C and D A. Incorrect: SMTP is a vital part of an e-mail installation, but it does not provide a mailbox service. All of its transactions are performed in real time by computers that are currently connected to the network. B. Incorrect: HTTP is the protocol used for Web client/server connections and has no direct participation in e-mail mailbox transactions. C. Correct: POP3 is currently the most popular of the e-mail protocols offering mailbox services. POP3 servers are designed to store mail messages for a limited time—until the client logs on and retrieves them, after which the messages are usually deleted. D. Correct: IMAP4 is a newer and more advanced mailbox protocol that enables clients to store their mail on the server permanently. This enables users to access their mail from any computer, any time.

N10-002.02.05.003

Correct Answers: D A. Incorrect: The amount of data exchanged by the two computers involved in a Telnet connection is usually quite limited. All messages are textual, with one computer sending commands and the other returning only the responses to those commands the operating system generates. Therefore, the speed of the connection between the two computers is not a major factor in the performance of the Telnet application. B. Incorrect: Telnet always uses TCP at the transport layer, which makes the question of which transport layer protocol to use irrelevant. C. Incorrect: The version of the operating system running on both of the connected computers has no effect on the degree of functionality provided during a Telnet session. D. Correct: Different computing platforms and operating systems have various capabilities built into the command line. UNIX, for example, can perform virtually all of its functions from the command line, meaning that Telnet enables an administrator to exercise almost complete control of the remote computer during a Telnet session. Windows, on the other hand, relies heavily on its graphical user interface (GUI) and has relatively little power at the command line. A Telnet user connecting to a Windows computer therefore has much more limited functionality than when connecting to a UNIX computer.

Objective 2.5

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N10-002.02.05.004

Correct Answers: A A. Correct: ICMP is a network layer (not application layer) protocol that TCP/IP systems use to carry diagnostic and error messages. B. Incorrect: Telnet is an application layer protocol use to execute commands on a computer from a remote location. C. Incorrect: NTP is an application layer protocol used to synchronize clocks on networked computers. D. Incorrect: FTP is an application layer protocol used to transfer files between computers and to perform basic file management tasks.

N10-002.02.05.005

Correct Answers: D A. Incorrect: The TFTP is a simple, yet specialized, protocol intended primarily for use by diskless workstations. Web browsers and servers never use TFTP. B. Incorrect: The NTP is used to synchronize the clocks on networked computers.Web browsers and servers do not use NTP. C. Incorrect: The SMTP is used by e-mail clients and servers, not by Web clients and servers. D. Correct: The HTTP is the application layer protocol that Web browsers use to send URLs to Web servers and that Web servers use to send the requested Web page files back to the browsers.


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O B J E C T I V E

2 . 6

Define the function of TCP/UDP ports. Identify well-known ports.

For the protocols at the various layers of the protocol stack to work together, they must be able to pass data to and from each other. When there is more than one protocol operating at a particular layer, the adjacent layers must specify which protocol should receive the data they are passing. For example, the Ethernet protocol, operating at the data-link layer, uses a value called an Ethertype to specify which network layer protocol generated the data carried as its payload. When a computer receives an Ethernet packet from the network, it reads the Ethertype value and passes the data up to the specified protocol at the network layer. In the same way, a network-layer protocol such as IP has a field in its header that specifies which transport layer protocol (TCP or UDP) generated its payload. At the transport layer, TCP and UDP do the same thing to specify the application that generated the payload data in their packet. The applications are identified using numerical values called ports. Each TCP and UDP packet contains a source port field and a destination port field, which reference the application or service that generated the data and that should receive the data, respectively. When one of the transport layer protocols receives a packet from IP at the network layer, it reads the value of the destination port field and passes the data in its payload to the application the port identifies. The values for the port fields come from two possible sources. The common server applications and services used on the Internet have permanently assigned port numbers, which are known as well-known ports. IANA assigns these values and they are published in the “Assigned Numbers” RFC (currently RFC 1700). TCP and UDP each have their own independent port number assignments. Just because an application uses a particular port with the TCP protocol does not necessarily mean that the UDP port number

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Readiness Review—Exam N10-002 with the same value refers to the same application. Some of the most commonly used well-known ports are listed in the following table. Application

Transport Layer Protocol

Well-Known Port

FTP (data)

TCP

20

FTP (control)

TCP

21

SMTP

TCP

25

POP3

TCP

110

IMAP4

TCP

143

HTTP

TCP

80

DNS

TCP and UDP

53

DHCP/BOOTP servers

UDP

67

DHCP/BOOTP clients

UDP

68

SNMP

UDP

161

Clients use the well-known port numbers to contact servers, but servers must also specify a port number when sending reply messages back to the client. In most cases, clients select their own port number for each transaction with a server and specify it in the source port field of the request messages they transmit. The server reads this value from the request messages and uses it to send its replies to the client. This type of randomly selected port value is called an ephemeral port. Because port values below 1,024 (0 through 1,023) are reserved for use as well-known ports, ephemeral port numbers always have a value of 1,025 or greater.

Objective 2.6

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Objective 2.6 Questions N10-002.02.06.001 Which well-known ports are typically used to configure the SMTP and POP3 services for an Internet e-mail client? (Choose two.) A. 25 B. 110 C. 143 D. 80

N10-002.02.06.002 Which of the following two pairs of port numbers would you use to configure the SMTP and POP3 server connections for an e-mail client? A. 110 and 143 B. 25 and 143 C. 110 and 161 D. 25 and 110

N10-002.02.06.003 Which component does a port number identify? A. A network layer protocol B. An application C. A data-link layer protocol D. A transport layer protocol

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N10-002.02.06.004 Which of the following values could be used by a client as an ephemeral port number? A. 1 B. 101 C. 1,024 D. 1,999


Correct Answers: A and B A. Correct: SMTP servers listen on port 25 for incoming connections from client computers and other SMTP servers. B. Correct: POP3 uses port 110 to listen for incoming connections from e-mail clients seeking to check their mailboxes. C. Incorrect: IMAP4 is another protocol providing mailbox services to e-mail clients, but it uses a different port (number 143) than POP3. D. Incorrect: Port 80 is reserved for Web servers running the HTTP protocol, and it has nothing to do with e-mail.

N10-002.02.06.002

Correct Answers: D A. Incorrect: 110 is the correct port number for POP3, but port 143 is used by IMAP4, another mailbox protocol. IMAP4 and POP3 are never used together. B. Incorrect: SMTP uses port 25, but port 143 is used by IMAP4. E-mail clients can use SMTP and IMAP4 together, but IMAP4 is not interchangeable with POP3. C. Incorrect: POP3 uses port 110, but port 161 is used by the Simple Network Management Protocol (SNMP), which has nothing to do with e-mail. D. Correct: Port 25 is used by SMTP and port 110 is used by POP3.

Objective 2.6

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N10-002.02.06.003

Correct Answers: B A. Incorrect: The protocols at each layer in the protocol stack contain a value that identifies the protocol at the layer above that generated the encapsulated data. Since port numbers are used at the transport layer and the network layer is below that, the port number cannot identify a network layer protocol. B. Correct: The transport layer protocol receives data from an application or service running on the computer and packages it before passing it down to the network layer. The port number identifies the application that generated the data. C. Incorrect: Protocols at a particular layer in the OSI model interact directly with only the layers immediately above and below it. Since port numbers are used by transport layer protocols, they cannot reference data-link layer protocols, which operate two layers below. D. Incorrect: The protocols that use port numbers, TCP and UDP, operate at the transport layer, and therefore have no need to reference a transport layer protocol.

N10-002.02.06.004

Correct Answers: D A. Incorrect: All values below 1,024 are reserved for use as well-known port numbers. B. Incorrect: All values below 1,024 are reserved for use as well-known port numbers. C. Incorrect: The value 1,024 is reserved by the IANA and is not used for either a well-known or an ephemeral port number. D. Correct: All values over 1,024 are available for clients as ephemeral port numbers.


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O B J E C T I V E

2 . 7

Identify the purpose of the following network services (e.g., DHCP/BOOTP, DNS, NAT/ICS, WINS, and SNMP).

TCP/IP networks rely on a variety of services that provide important administrative functions to the computers. Some of these services are:

Dynamic Host Configuration Protocol (DHCP)/Bootstrap Protocol (BOOTP)—DHCP and BOOTP are both services that automatically configure the operational parameters for a TCP/IP client, such as the IP address, subnet mask, and default gateway. DHCP and BOOTP provide a valuable service to network administrators because they would otherwise have to configure each TCP/IP client manually and retain a record of each computer’s settings to avoid IP address duplication. BOOTP is a progenitor of DHCP, which requires an administrator to configure the server with settings for each individual client. DHCP takes this concept a step further by dynamically assigning addresses from a common pool called a scope and reclaiming them when they are not used for a given period of time. Domain Name System (DNS)—TCP/IP computers identify each other using IP addresses and use these addresses to direct packets to their destinations. However, alphabetical names are easier for people to use, and the DNS provides a name space for Internet computers as well as a service for resolving DNS names into IP addresses. The DNS name space consists of domain names, such as microsoft.com, which have two or more levels, and host names, which identify specific computers in a domain. The DNS name www.microsoft.com, for example, refers to a host called www in the microsoft.com domain. Whenever a program on a TCP/IP client computer requests access to a server by name, the client uses a DNS server to convert that name to an IP address before sending any packets to the destination server. This process is called name resolution. DNS servers contain information about domains and hosts in units called resource records. If a client’s DNS server has a resource record containing the IP address associated with the requested server

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Readiness Review—Exam N10-002 name, it supplies it to the client. If not, the DNS server relays the request to another server (sometimes more than once) until it locates the required information.

Network Address Translation (NAT)—Computers that are connected to the Internet normally must have an IP address that has been registered with the IANA. This prevents address duplication on the Internet and enables Internet systems to access the computer. For networked computers that connect to the Internet only as clients, however, registered addresses aren’t necessary and leave the system open to attack from Internet vandals. NAT is a service that enables the computers to use unregistered IP addresses and still access the Internet as a client. NAT is implemented as a server located between the client computer and the Internet. The NAT server has a registered IP address and the client has a private, unregistered address. As a result, the client is invisible to the Internet and safe from attack. The client is configured to use the NAT server as its default gateway, and when the client attempts to access an Internet service, the request goes to the NAT server. Prior to forwarding the request to the Internet server, NAT modifies it by substituting its own registered IP address for the client’s unregistered one in the IP header. Because the Internet server receives a request containing a registered IP address, it can respond normally, sending the reply to the NAT server. The NAT server then relays the response to the client that originated the request. NAT can be implemented in hardware or software, and is integrated into many Internet access router products, including the Internet Connection Sharing (ICS) feature found in the latest versions of Microsoft Windows. Windows Internet Naming Service (WINS)—Microsoft Windows networks have traditionally used NetBIOS names to identify computers on a network. It was only with the release of Windows 2000 that the DNS name space began to replace the NetBIOS name space. Like DNS names, NetBIOS names must be resolved into IP addresses before communication can take place on a TCP/IP network. WINS is a service included in all Windows 2000 Server and Windows NT 4 Server products that maintains a database of the NetBIOS names on a network and their IP addresses, and resolves names when clients request it. (Although a Windows 2000/ Active Directory network uses DNS names instead of NetBIOS names, WINS is still included to support clients running earlier versions of Windows.) WINS servers can replicate their data to each other to provide reliable name resolution services for an entire enterprise network.

Objective 2.7

89

Simple Network Management Protocol (SNMP)—SNMP is a service that enables network administrators to gather information about applications and devices located all over the network and view it at a central network management console. SNMP agents, embedded into hardware products and integrated into software, gather information about the status and performance of the application or device and store it in a Management Information Base (MIB). The agents transmit the information periodically to a network management console application, such as Hewlett-Packard’s Open View, which collates it and displays it in various ways. In addition to these scheduled updates, agents can also generate messages called traps, which they transmit immediately to the console or pager to inform it that a serious condition exists on the network.

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Objective 2.7 Questions N10-002.02.07.001 Which of the following services are used to resolve names into IP addresses? (Choose two.) A. BOOTP B. WINS C. SNMP D. DNS

N10-002.02.07.002 Faced with the task of installing and configuring 100 new computers, Bob, a new network administrator, seeks to make the job as easy as possible. Which of the following services will provide Bob with the most help in accomplishing his task? A. NAT B. BOOTP C. DNS D. DHCP

N10-002.02.07.003 Which of the following services is useful only on networks that are connected to the Internet? A. DNS B. DHCP C. NAT D. SNMP

Objective 2.7

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Correct Answers: B and D A. Incorrect: BOOTP is an ancestor of DHCP, and it is used to automatically configure the TCP/IP clients on networked computers. It has nothing to do with the name resolution process. B. Correct: WINS servers resolve the NetBIOS names often used on Windows networks into the IP addresses needed for TCP/IP communications. C. Incorrect: SNMP is used to gather and transmit network management information to a central console and does not participate in the name resolution process. D. Correct: DNS servers resolve host and domain names into the IP addresses needed for TCP/IP communications.

N10-002.02.07.002

Correct Answers: D A. Incorrect: NAT can help Bob provide his network users with Internet access using unregistered IP addresses, but it does not aid in the installation or configuration of network workstations. To use NAT, each computer must be configured with an unregistered IP address and with a NAT server as its default gateway. B. Incorrect: BOOTP can definitely help Bob set up his new computers without having to travel to each machine by automatically configuring their TCP/IP client parameters. However, before BOOTP can configure the workstations, Bob must manually enter the TCP/IP parameters for each client in the BOOTP server. C. Incorrect: The DNS name resolution service will be useful to the new computers after they are installed, but it does not aid in the installation or configuration process. Before it can use DNS, each TCP/IP client must be configured with the address of one or more DNS servers. D. Correct: Like BOOTP, DHCP can help Bob set up the new computers by automatically configuring the TCP/IP clients. Unlike BOOTP, however, DHCP can automatically assign IP addresses to the computers from a range of addresses that Bob enters into the server. This eliminates the need to manually specify the TCP/IP parameters for each client and provides Bob with substantially more help in his task than BOOTP does.

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N10-002.02.07.003

Correct Answers: C A. Incorrect: Although DNS is traditionally associated with the Internet, it can perform its functions on a private network, too. Many private UNIX networks rely on DNS, and Microsoft’s Active Directory Services also uses DNS servers on private networks to store information about the network and to enable computers to locate domain controllers. B. Incorrect: DHCP is designed to aid in the configuration of TCP/IP computers on private networks and its usefulness is not affected positively or negatively by the network’s connection to the Internet. C. Correct: NAT enables computers on an unregistered network to access Internet services just as if they were registered. If a network is not connected to the Internet, it has no use for NAT. D. Incorrect: SNMP gathers information about devices and applications on a private network and is not affected by an Internet connection.

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O B J E C T I V E

2 . 8

Identify IP addresses (IPv4, IPv6) and their default subnet masks.

IP addresses are 32 bits long and consist of a network identifier and a host identifier, but the number of bits devoted to each of these values is not always the same. The function of the subnet mask is to indicate which bits identify the network and which the host. Normally, IP addresses are expressed as four 8-bit decimal values known as octets separated by periods (for example, 192.168.5.26). When you express the IP address and the subnet mask as binary values and compare them, the 1 bits of the mask indicate that the corresponding bits in the IP address are the network identifier bits. The 0 bits in the mask indicate the host identifier bits in the address. The IP addresses that Internet computers use must be registered with the IANA. To do so, a network administrator obtains a registered network address and assigns the host values to the computers on the network. The IANA offers three classes of network addresses, which support different numbers of hosts and use different subnet masks. These three address classes are shown in the following table. Class A

Class B

Class C

Host Address Bits

24

16

8

Subnet Mask

255.0.0.0

255.255.0.0

255.255.255.0

Addresses Begin with: (Binary)

0

10

110

First Byte Values (Decimal)

0–127

128–191

192–223

Number of Networks

127

16,384

2,097,151

Number of Hosts

16,777,214

65,534

254

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Readiness Review—Exam N10-002 When an organization registers a Class C address (usually with an ISP and not with the IANA directly), it can create a network of up to 254 devices using the 8 host identifier bits. (The 8-bit host identifier supports only 254 devices instead of 256 [28] because the values 0 and 255 cannot be used to represent individual hosts.) Each device has an IP address that consists of the same 24 network identifier bits (starting with a decimal value between 192 and 223), a unique host identifier, and a subnet mask of 255.255.255.0. For a network with more than 254 computers, an organization can obtain all or part of a Class B address, which has 16 host identifier bits and therefore supports up to 65,534 devices. The 32-bit IP addresses in use today are IP, version 4 (or IPv4) addresses. IP, version 6 (IPv6) is in development and will increase the address space from 32 bits to 128 bits. IPv6 addresses are notated differently than IPv4 addresses. Instead of four 8-bit decimal values, an IPv6 address consists of eight 16-bit hexadecimal values separated by colons (for example, FEDC:BA98:7654:3210:FEDC:BA98:7654:3210).

Objective 2.7

Objective 2.8 Questions N10-002.02.08.001 Which of the following is a valid Class B address? A. 14.2.26.119 B. 127.0.0.1 C. 131.2.19.56 D. 193.46.87.44

N10-002.02.08.002 Which of the following IP addresses cannot be assigned to a network host? (Choose two.) A. 19.224.5.16 B. 224.1.87.12 C. 1.1.1.1 D. 193.256.64.12

N10-002.02.08.003 How many bits are devoted to the network identifier in a Class A IP address? A. 8 B. 16 C. 24 D. 32

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N10-002.02.08.004 As the new administrator of a TCP/IP network consisting of 300 computers, you are responsible for completing a planned project to connect the network to the Internet. The previous network administrator has already registered a Class C network IP address for this purpose. Which of the following courses of action could you take to complete the project? (Choose two.) A. Proceed as planned with no alterations. B. Switch to the IPX/SPX protocol suite instead of TCP/IP. C. Register a second Class C address. D. Add a NAT server to the network.


Correct Answers: C A. Incorrect: IP addresses with a value of 0 to 127 as their first byte are Class A addresses. B. Incorrect: This address, known as a loopback address, is used to test a TCP/IP implementation by transmitting traffic to itself, and it is not valid for use by a workstation. The value of the first byte (127) also falls into the Class A range. C. Correct: The value of this address’s first byte (131) falls into the range allotted to Class B, making it a valid Class B address. D. Incorrect: The value 193 as the first bytes places this address in the Class D range.

N10-002.02.08.002

Correct Answers: B and D A. Incorrect: This is a valid Class A address that can be assigned to a host on the network. B. Correct: The first byte of this address (224) falls outside of the Class A, B, and C ranges and cannot be assigned to a host. The first byte values from 224 to 239 are reserved for use in Class D addresses, which are multicast addresses that represent a group of devices on the network, not individual hosts. For example, the multicast address 224.0.0.2 is used to send traffic to all of the routers on the network.

Objective 2.8 C. Incorrect: Despite its odd appearance, this is a perfectly valid Class A address. D. Correct: This is an invalid IP address because the value of the second byte is 256, which cannot be represented by an 8-bit binary value.

N10-002.02.08.003

Correct Answers: A A. Correct: A Class A address has an 8-bit network identifier and a 24-bit host identifier. B. Incorrect: An address with a 16-bit network identifier (and therefore a 16-bit host identifier) is a Class B address. C. Incorrect: An address with a 24-bit network identifier (and therefore an 8-bit host identifier) is a Class C address. D. Incorrect: No IP address can possibly have a 32-bit network identifier because that leaves no bits for a host identifier.

N10-002.02.08.004

Correct Answers: C and D A. Incorrect: A single Class C network address supports a maximum of 254 nodes, making it insufficient to connect the entire 300 node network to the Internet. Proceeding as planned would not be possible. B. Incorrect: The IPX/SPX protocols are for use on LANs only and cannot provide access to the Internet, making this an unviable solution. C. Correct: A second Class C network address would make it possible to connect all 300 computers to the Internet. D. Correct: Adding NAT would eliminate the need for the registered IP addresses that the Class C address provides and enable you to connect any number of computers to the Internet using unregistered addresses. NAT also provides greater security for the network by rendering the client computers invisible to potential Internet intruders.

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O B J E C T I V E

2 . 9

Identify the purpose of subnetting and default gateways.

Class C IP addresses support networks of up to 254 nodes, which is sufficient for a small- to medium-sized network. When you move up to a Class B address, however, you can have up to 65,534 nodes. Few organizations have networks this large, and no single network has the 16,777,214 nodes needed to take full advantage of a Class A network. To make using Class A and B (and even C) networks practical for organizations of all sizes, it is possible to split the network into smaller pieces called subnets. A subnet is simply a subset of a network address. By splitting a Class B network address into subnets, for example, a large organization can create separate networks for each of its office locations. Subnetting is also how ISPs make registered IP addresses available to their clients. An ISP can conceivably register a Class B address and split it into subnets, each of which it assigns to a different client. To split an existing network address into subnets, you borrow some of the host identifier bits to create a subnet identifier. For example, if you take eight of a Class B address’ 16 host identifier bits to create a subnet identifier, you make it possible to create 254 (28-2) subnets of 254 nodes each, instead of one network of 65,534 (216-2) nodes. To use a subnetted network address, you have to modify the subnet mask to include the borrowed subnet bits in the network identifier. For the subnetted Class B address in this example, you would change the mask from 255.255.0.0 to 255.255.255.0. If you subnet the Class B network address 172.16.0.0, the IP addresses for the first subnet would run from 172.16.1.1 to 172.16.1.254; the second subnet would run from 172.16.2.1 to 172.16.2.254, and so on. The size of the subnet identifier does not have to be 8 bits. You can borrow as many bits from the host identifier as you want to create the number of subnets you need. However, the process of calculating the IP address and subnet mask values is considerably more complex when you are working with other subnet configurations.

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Readiness Review—Exam N10-002 Subnetting is the only reason subnet masks are needed. If networks used only Class A, B, and C network addresses without modification, applications could differentiate between the network and host identifiers simply by examining the values of the IP address’ first three bits. In the language of the TCP/IP protocols, gateway is synonymous with router. When your network consists of more than one LAN and/or is connected to the Internet, each computer should have a default gateway address specified as part of its TCP/IP configuration. The default gateway is the router that the computer should use to access resources on other networks when no specific route exists. Every TCP/IP computer has a routing table that contains information about the other LANs on the internetwork and how to access them. When the computer has a packet to transmit, the IP protocol searches the routing table for an entry corresponding to the packet’s destination address. If there is no entry for that particular destination, IP uses the router identified by the default gateway entry to transmit the packet. Client workstations typically use the default gateway for most, if not all, of their internetwork communications.

Objective 2.9

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Objective 2.9 Questions N10-002.02.09.001 Which of the following best describes the process of subnetting on a TCP/IP network? A. You borrow bits from the network identifier to create a subnet identifier. B. You borrow bits from the host identifier to create a subnet identifier. C. You borrow half of the subnet identifier bits from the network identifier and half from the host identifier. D. You extend the IP address by adding bits for a subnet identifier.

N10-002.02.09.002 What is the maximum number of subnets you can create on a Class A network if you use 16-bit subnet identifiers? A. 254 B. 65,534 C. 65,536 D. 16,777,214

N10-002.02.09.003 The term default gateway refers to which type of networking component? A. An Internet access modem B. A switch C. A router D. A hub

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Correct Answers: B A. Incorrect: The network identifier must remain intact for packets to be routed to the network properly. B. Correct: By reducing the number of host identifier bits and using the borrowed bits as a subnet identifier, you can split your network into multiple subnets, each consisting of a smaller number of hosts. C. Incorrect: You cannot remove bits from the network identifier, so all of the subnet identifier bits must come from the host identifier. D. Incorrect: The IP protocol and all of the networks that use TCP/IP rely on a consistent 32-bit IP address space. The overall length of the address cannot be changed.

N10-002.02.09.002

Correct Answers: B A. Incorrect: An 8-bit subnet identifier would enable you to create 254 subnets, not a 16-bit one. B. Correct: The number of subnets you can create using a subnet identifier of a particular length is computed using the formula 2 to the x power minus 2. C. Incorrect: The minimum and maximum values (0 and 65,535, respectively, for a 16-bit subnet identifier) are always omitted from a subnet identifier calculation (which explains the –2 in the formula). D. Incorrect: A 24-bit subnet identifier would be required to create this many subnets.

N10-002.02.09.003

Correct Answers: C A. Incorrect: While a modem may be the interface that provides access to the Internet, it does not route network traffic, so it cannot be the default gateway. B. Incorrect: Switches operate at the data-link layer of the OSI reference model and also do not route traffic between networks, so a switch cannot be the default gateway. C. Correct: A router, by definition, connects networks and forwards traffic between them. The default gateway is a router that provides access to the rest of the internetwork. D. Incorrect: Hubs are physical layer devices that have nothing to do with routing traffic between networks, so a hub cannot be the default gateway.

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O B J E C T I V E

2 . 1 0

Identify the differences between public vs. private networks.

A public network is one that is connected to the Internet and uses IP addresses that are registered with the IANA. This makes the computers on the network visible to the Internet and vulnerable to attack. Public, however, does not mean that the network is left wide open to access by any Internet user. Public networks are typically protected by various types of firewalls, which are available as either software or hardware solutions and are located between the network and the Internet. For a network with users who access the Internet as clients only, a public network with registered IP addresses is not necessary and can present a genuine risk, even with a firewall in place. Internet vandals are constantly working on new ways to penetrate the security protecting registered networks, and there are many different technologies available to provide client access to the Internet without using registered addresses. The computers that do have to be on a public network are those that function as Internet servers, such as Web and e-mail servers that have to remain continuously available to Internet clients. The computers must have registered IP addresses because clients locate them using DNS, which resolves the name of a server to its address. Protecting Internet servers is more difficult for this reason. If the entire network is public and protected by a firewall, the Internet servers may be located outside the firewall to avoid compromising the security of the client network. A private network is one that uses IP addresses that are not registered with the IANA. When a computer’s IP address is unregistered, it is functionally invisible to the Internet, which makes it impossible for Internet vandals to access the computer. When a private network is not connected to any other network or to the Internet, you can use any network addresses you want as long as no two computers have duplicate IP addresses. However, if the network is connected to the Internet, using IP addresses that are registered to some other organization can prevent your clients from accessing the Internet services using those same addresses. As a result, the IANA has reserved three ranges of addresses for use by private networks—one for each address class. These address ranges are not registered to any one organization, so there is no chance of a conflict

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Readiness Review—Exam N10-002 between a computer on your network and an Internet computer with the same address. The reserved private address ranges are listed in the following table. Class

Range of addresses

A

10.0.0.0 to 10.255.255.255

B

172.16.0.0 to 172.31.255.255

C

192.168.0.0 to 192.168.255.255

To use these network addresses, you either create a subnet or use them as is. For example, to use the Class C address, you would create a subnet by assigning the third byte a value from 1 to 254 and using the standard Class C subnet mask: 255.255.255.0. To use the Class B address, you can either create a subnet by assigning a value to the third byte and using the Class C subnet mask, or you can use the Class B subnet mask (255.255.0.0) and simply start assigning addresses to your workstations. For the computers on a private network to access the Internet using their unregistered IP addresses, you must use a service designed for this purpose, such as NAT or a proxy server. Without an intervening service, the unregistered client can send messages to an Internet server but the server cannot respond. Both NAT and proxy servers place a computer with a registered IP address between the client and the Internet and modify the clients’ request messages to make them appear as though they came from the registered computer (making the request on the clients behalf). This enables the Internet server to respond to the requests in the usual manner, and the NAT or proxy server relays the responses to the clients.

Objective 2.10

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Objective 2.10 Questions N10-002.02.10.001 Which of the following IP addresses are suitable for use by a workstation on a private network? (Choose two.) A. 199.224.76.14 B. 172.16.3.224 C. 10.255.255.255 D. 192.168.128.253

N10-002.02.10.002 Which of the following services enables the computers on private networks to function as Internet clients? (Choose two.) A. The DNS B. The IANA C. NAT D. Proxy server

N10-002.02.10.003 Which of the following devices protects the computers on a public network from Internet intruders? A. A firewall B. A router C. A proxy server D. A NAT server

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Correct Answers: B and D A. Incorrect: This Class C address does not fall within the range of Class C addresses reserved for use on private networks, which all begin with 192.168. B. Correct: This address falls within the range of Class B addresses reserved for private networks. C. Incorrect: Although this address falls within the range of Class A addresses reserved for private networks, the host identifier consisting of all 1’s (in binary form, or 255.255.255 in decimal form) is reserved and cannot be assigned to a workstation. D. Correct: This address falls within the range of Class C addresses reserved for private networks.

N10-002.02.10.002

Correct Answers: C and D A. Incorrect: Computers on the Internet use the DNS to resolve names into IP addresses. Since unregistered IP addresses do not exist in the DNS, they cannot provide Internet connectivity to clients on private networks. B. Incorrect: The IANA is responsible for registering IP address assignments. The IANA has reserved the address ranges used for private networks, but it does nothing to provide Internet connectivity for computers using those addresses. C. Correct: NAT is a network layer service that enables computers with unregistered IP addresses to access Internet services by relaying their requests through a NAT server. D. Correct: A proxy server is an application layer service that enables clients on private networks to access the Internet by making the request on the clients’ behalf.

N10-002.02.10.003

Correct Answers: A A. Correct: Firewalls, located between public networks and the Internet, use a variety of techniques to protect computers with registered IP addresses from unauthorized Internet users. B. Incorrect: Routers provide a public network with access to the Internet, but in their pure form they provide no protection. In some cases, firewall functions can be incorporated into a router product. C. Incorrect: Proxy servers protect computers on private networks from Internet intrusion. D. Incorrect: NAT servers protect computers with unregistered IP addresses from Internet intruders.

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O B J E C T I V E

2 . 1 1

Identify the basic characteristics (e.g., speed, capacity, media) of the following WAN technologies: packet switching vs. circuit switching, ISDN, FDDI, ATM, Frame Relay, SONET/SDH, T1/E1, T3/E3, OCx.

Wide area network (WAN) links are used to connect LANs at remote locations and to connect networks to the Internet. Unlike a LAN, a WAN is usually a point-to-point link between two locations, so there is no shared network medium and no need for MAC. The need to share a network medium is one of the primary reason LANs are packetswitching networks. A packet-switching network is one in which the data to be sent over the network is broken up into small units called packets, which are transmitted individually. Once the packets reach their destination, the receiving system reassembles them into their original form. Packet switching prevents a single device with a lot of data to transmit from monopolizing the network for a long time, and it provides each device an equal opportunity to transmit. The opposite of packet switching is circuit switching. A circuit-switching network is one in which computers establish a circuit between them before they transmit data. The circuit stays open during the life of the session, enabling the computers to send their data as a continuous stream. The classic example of a circuit-switching network is the telephone system. By dialing a number, you establish a connection to another party. Once the connection is established, the transfer of data (speech) proceeds until the circuit is broken. Circuit switching is impractical on a baseband network such as a LAN, but it is used by many WAN technologies. A WAN connection can be as simple as two standard modems and a telephone line, but more bandwidth is usually required for connecting networks. Some of the most common WAN technologies are:

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Integrated Services Digital Network (ISDN)—ISDN is a digital service that uses your facility’s existing telephone wiring to provide transfer speeds of up to 128 Kbps with its Basic Rate Interface (BRI) service. ISDN is unusual because it is not a permanent connection between two points, but a dial-up service that you can use to connect to different locations at will. Fiber Distributed Data Interface (FDDI)—FDDI is a data-link layer protocol that uses fiber optic cable and runs at 100 Mbps. FDDI can operate on a LAN because it uses a shared network medium and the token passing method of MAC. However, fiber optic cables can span much longer distances than the copper cables used on most LANs, so it is also possible to use FDDI as a WAN protocol. A FDDI WAN can’t connect networks in other cities, but it can connect networks located in buildings on the same campus. Asynchronous Transfer Mode (ATM)—ATM is also a protocol that can operate on LANs or WANs, but it is more commonly used for WAN links. Unlike most protocols, which use frames of varying sizes, ATM uses cells that are always 53 bytes long. ATM is a switched, connection-oriented, full-duplex, point-to-point service that runs on a variety of media types at many different speeds, ranging from 25.6 Mbps to 2.46 Gbps. ATM connections can use standard multimode fiber optic or unshielded twisted pair cables at the physical layer, as well as other services, such as leased lines and Synchronous Optical Network (SONET). Leased lines—A leased line is a permanent telephone connection between two points that provides a fixed amount of bandwidth around the clock. Leased lines can be analog or digital, but most of the connections are digital. Telephone companies provide leased lines at various speeds, which are classified in the United States using T-carrier levels and in Europe using E-carrier levels. Prices are based on the speed of the connection and the distance between the two sites. The most popular service in the U.S. is the T-1, which runs at 1.544 Mbps. The European equivalent is called an E-1 and runs at 2.048 Mbps. For organizations requiring more bandwidth, the T-3 and E-3 services run at 44.736 Mbps and 34.368 Mbps, respectively.

Objective 2.11

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Frame Relay—Frame relay is an alternative to connecting two sites with a permanent, long-distance, fixed-bandwidth leased line. Leased lines provide the same bandwidth at all times, which means that most customers are paying for bandwidth they are not using, for at least part of the day. In a frame relay connection, both sites are connected to the service provider’s nearest point of presence (POP), typically using a short-distance leased line. Once the data from the two sites arrives at the POP, the service provider routes the traffic through its own network, called a cloud, using virtual circuits. The advantage of frame relay is that it can provide a flexible amount of bandwidth based on the time of day or any other criteria. With a leased line, the only way to exceed the bandwidth the connection provides is to install another line. With frame relay, you contract with your service provider for an average amount of bandwidth that enables you to have bursts of high traffic that exceed your nominal bandwidth. If you need even more speed as your network traffic increases, you simply pay a higher fee. Frame relay also enables you to connect networks at multiple sites to the same cloud and route traffic between all of them at the same time using only one leased line at each site. Synchronous Optical Network (SONET)/Synchronous Digital Hierarchy (SDH)—SONET is a physical layer standard for the construction of a synchronous telecommunications network using fiber optic cables. SDH is the international equivalent of SONET. Intended as a replacement for the T-carrier and E-carrier services, SONET provides many levels of service at different speeds, which are named using Optical Carrier (OC) designations. OC-1 runs at 51.84 Mbps and speeds increase from there. An OC-192 connection runs at 9,952 Mbps. Because of these designations, the SONET/SDH services are sometimes called OCx.

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Objective 2.11 Questions N10-002.02.11.001 Which of the following WAN technologies provides a dial-up service? A. T-1 B. ATM C. ISDN D. SONET

N10-002.02.11.002 Which of the following technologies provides leased line services in Europe? A. The E-carrier service B. Frame relay C. SDH D. ISDN

N10-002.02.11.003 Which of the following are examples of circuit switching? (Choose three.) A. A voice telephone call B. A frame relay connection C. An ATM connection D. An ISDN connection

N10-002.02.11.004 Which of the following WAN technologies provides the most bandwidth? A. T-3 B. FDDI C. ISDN’s BRI D. OC-1

Objective 2.11

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Correct Answers: C A. Incorrect: A T-1 is a leased line that provides a permanent connection between two points. Because the connection is permanent, there is no dial-up service. B. Incorrect: ATM is a switched service that runs over a variety of physical media, but none of these provide dial-up service. C. Correct: ISDN is a dial-up telephone service that provides digital communications and higher bandwidth using standard telephone wiring. D. Incorrect: SONET is a standard for a fiber optic telecommunications network, but it is designed to replace permanent connection technologies such asT-1s and E-1s, not dial-up telephone service.

N10-002.02.11.002

Correct Answers: A A. Correct: The E-carrier service is the European equivalent of the T-carrier service in the United States and provides different levels of leased line service, such as E-1 and E-3. B. Incorrect: Frame relay is an alternative to leased line services that provides more flexible bandwidth options using a network called a cloud. C. Incorrect: SDH is the international equivalent of the SONET standard, which defines a telecommunications network that is designed to replace the E-carrier service in Europe. D. Incorrect: ISDN is a popular alternative to leased line services in Europe that provides digital dialup connections at varying speeds.

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N10-002.02.11.003

Correct Answers: A, B, and D A. Correct: A voice telephone call begins with the establishment of a circuit between the two participants, which is triggered by the dialing of a telephone number. The circuit remains in place until one of the parties ends the call. B. Correct: Frame relay uses virtual circuits through the service provider’s cloud, which must be established before any data is transmitted between two end sites. C. Incorrect: ATM uses an alternative to packet switching called cell switching. The only difference is that ATM uses fixed-length cells instead of variable-length packets. D. Correct: ISDN is a dial-up service just like the standard voice telephone network, and it requires you to dial a number to establish a circuit to the destination before transmitting any data.

N10-002.02.11.004

Correct Answers: B A. Incorrect: A T-3 connection runs at 44.736 Mbps, less than half the speed of a FDDI connection. B. Correct: At 100 Mbps, FDDI is by far the fastest of the WAN technologies discussed in this domain. However, FDDI’s great speed is mitigated by the fact that it is limited to relatively short campus connections, while the other technologies can span virtually any distance. C. Incorrect: ISDN’s BRI service runs at only 128 kilobits (not megabits) per second, making it far slower than all of the other WAN technologies. D. Incorrect: An OC-1 connection runs at 51.84 Mbps—faster than a T-1, but not as fast as FDDI.

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O B J E C T I V E

2 . 1 2

Define the function of the following remote access protocols and services: RAS, PPP, PPTP, ICA.

Remote access is the capability to connect to network resources from a long distance, typically using modems and telephone lines. When a standalone computer dials in to an ISP to access the Internet, this is an example of remote access. Many corporate networks also provide remote access capabilities to enable users working from home or traveling to access their business e-mail, corporate databases, or company documents from wherever they are. On a smaller scale, individual users can also configure their computers to provide remote access, enabling them to dial in from home or from a hotel room. Remote access is a client/server arrangement in which a computer connected to the network is configured to function as a remote access server and a standalone computer at another location is the remote access client. Dialing in to the remote server enables the client to access the resources on the server computer. To provide access to resources on the network, the remote access server must also function as a router. Most operating systems include the software required to support remote access, on the client, if not the server, level. On Windows 2000 and Windows NT computers, remote access is provided by the Remote Access Service (RAS). Windows 2000 and Windows NT include both a RAS client and a RAS server and can route all of the protocols they support. This enables you to use a Windows 2000/Windows NT computer at both ends of the remote access connection. The other Windows operating systems also include RAS clients that can access the Windows 2000/Windows NT RAS server. Windows 2000 Professional and Windows NT Workstation support a single remote access connection, while the Windows 2000 and Windows NT Server products can support up to 256 remote users at once. The Routing and Remote Access Service (RRAS), included with Windows 2000 Server and available as a free add-on to Windows NT Server, provides a single interface to all of the remote access server functions.

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Readiness Review—Exam N10-002 The connection between a remote access server and a client typically uses the Point-toPoint Protocol (PPP) at the data-link layer. PPP is a TCP/IP protocol that enables computers to communicate using a variety of network layer protocols. Unlike the data-link layer protocols used on LANs, PPP connects only two computers, so there is no shared network medium and no need for many of the functions traditionally associated with the data-link layer, such as addressing and MAC. During the PPP connection establishment process, the two computers negotiate a set of common features they will use to communicate, such as specific network layer protocols and authentication protocols. PPP is not associated with any particular physical layer standard; PPP can use a dial-up modem connection, leased lines, or any one of many other WAN technologies. Remote network access over long distances can be an expensive proposition no matter which type of WAN connection is involved. If you set up a RAS server on your network for traveling users, the long distance telephone charges can be considerable if the users are traveling to distant locations. Virtual Private Networks (VPNs) are a means of providing remote network access without incurring long distance telephone charges. A VPN is a WAN connection that uses the Internet as a network medium. Instead of dialing into the RAS server directly, the remote user dials into a local ISP instead and connects to the Internet. In the same way, the RAS server is connected to the Internet through a local provider. The two computers then establish a connection through the Internet, enabling the remote user to access the home network. To protect the data as it travels across the Internet, the computers use a technique called tunneling, which requires a special protocol such as the Point-to-Point Tunneling Protocol (PPTP). PPTP operates at the data-link layer and creates what is essentially a secured tunnel through the Internet.To use the tunnel, the computers violate the rules of the data encapsulation process by taking the PPP frames that the computers would normally transmit to each other, encapsulating them inside IP datagrams, and sending them inside PPTP frames. Another form of remote network access called thin-client/server computing enables users to run server applications on virtually any computer, regardless of its platform or operating system. The Independent Computing Architecture (ICA) developed by Cyrix Systems, Inc., is a combination of a server software component, a networking protocol, and a client application. A client connects to the server and launches an application that runs wholly on the server. The protocol carries keystrokes, mouse actions, and screen updates between the two computers, so the application appears to be running on the client computer but is actually running on the server.

Objective 2.12

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Objective 2.12 Questions N10-002.02.12.001 How does the tunneling technique used in virtual private networking violate the rules of data encapsulation? A. By eliminating the network layer protocol B. By encapsulating a data-link layer protocol inside a network layer protocol C. By encapsulating a network layer protocol inside a data-link layer protocol D. By eliminating the data-link layer protocol

N10-002.02.12.002 A network administrator is instructed to set up a remote access environment so users can log on to the corporate network from their home computers. After evaluating the technologies available, the administrator elects to create VPNs for the home users by connecting the RAS server to the Internet, providing the users with ISP accounts for their home computers, and installing PPTP support on all of the computers involved. Which of the following statements best evaluates the efficacy of this plan? A. This is the best solution available and should be implemented with no changes. B. The administrator should create VPNs, but using the ICA protocol instead of PPTP. C. The administrator should not use VPNs and should instead implement a standard RAS solution using dial-up modems and telephone lines. D. The administrator should create VPNs, but using the PPP protocol instead of PPTP.

N10-002.02.12.003 Which of the following are advantages of virtual private networking? (Choose two.) A. Economy B. Security C. Simplicity D. Orthodoxy

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Correct Answers: B A. Incorrect: IP, running at the network layer, is an essential component of the TCP/IP protocol stack and cannot be eliminated. B. Correct: Tunneling encapsulates PPP frames inside IP datagrams, and it is usually the IP datagram that is encapsulated within a PPP frame. C. Incorrect: Encapsulating a network layer protocol inside a data-link layer protocol is normal. D. Incorrect: A data-link layer protocol is required for TCP/IP computers to transmit data over a network. In fact, a VPN uses two data-link layer protocols: PPTP, to form the tunnel through the Internet, and PPP, which is carried inside the tunnel.

N10-002.02.12.002

Correct Answers: C A. Incorrect: VPNs are designed for situations in which direct RAS connections are not viable economically. Using VPNs for users within the local calling area is needlessly complex and even more expensive than direct RAS connections. B. Incorrect: The ICA protocol is not a replacement for PPTP and cannot be used for VPNs. C. Correct: A dial-up RAS solution provides the most efficient and economical RAS for nearby users. D. Incorrect: By itself, PPP is incapable of implementing the tunneling technique needed to protect the network data as it passes over the Internet.

N10-002.02.12.003

Correct Answers: A and B A. Correct: VPNs are an economical solution in long distance remote access situations because both the server and the client connect to a local ISP instead of using long distance telephone connections. B. Correct: VPNs encapsulate the network data inside a tunneling protocol that secures it from interception by other Internet users. C. Incorrect: VPNs are more complex to set up and administer than standard RAS connections. D. Incorrect: VPNs are decidedly unorthodox because they encapsulate data-link layer frames inside network layer datagrams.

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2 . 1 3

Identify the following security protocols and describe their purpose and function: IPsec, L2TP, SSL, Kerberos.

Security is an essential element of every network, and operating systems use a variety of security protocols to protect data as it is transmitted. Some of these protocols are:

IP Security Protocol (IPsec)—IPsec is a series of draft standards that define a means of securing data as it is transmitted over a LAN using authentication and encryption. IPsec consists of two separate protocols: the IP Authentication Header (AH) protocol and the IP Encapsulating Security Payload (ESP) protocol. AH inserts an additional header into IP datagrams after the IP header and before the transport layer protocol header. The AH header contains a sequence number that prevents unauthorized computers from replying to the datagram and an integrity check value (ICV) that the destination computer uses to verify that incoming datagrams have not been modified. ESP encapsulates the transport layer data in its own header and trailer and encrypts it. IPsec provides end-to-end security for networked computers, meaning that the source computer encrypts the data and it remains encrypted until it reaches the destination computer. Both computers must be running IPsec. Because the modifications that the AH and ESP protocols make are all inside the datagrams, the routers on the network do not have to support IPsec. Layer 2 Tunneling Protocol (L2TP)—L2TP is a virtual private networking protocol derived from Cisco Systems’ Layer 2 Forwarding protocol and PPTP. L2TP is a data-link layer protocol that computers can use to create a tunnel across the Internet, protecting the data inside. L2TP differs from PPTP in that the PPP frames the computers generate are encapsulated inside transport-layer UDP datagrams instead of IP datagrams. L2TP provides no encryption service of its own, but the UDP datagrams are usually encapsulated by the IPsec ESP protocol, which encrypts the data inside. L2TP also supports the use of multiple network layer

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Readiness Review—Exam N10-002 protocols inside the tunnel and provides flow control, while PPTP is an IP-only solution and has no flow control capabilities.

Secure Sockets Layer (SSL)—SSL is another protocol designed to protect data as it is transmitted over a network, but it is more specialized. SSL encrypts only the data exchanged by Web servers and clients, usually over the Internet. When you perform an e-commerce transaction on the Web, in most cases it is SSL that is securing the data. SSL consists of two protocols: the SSL Handshake Protocol (SSLHP), which provides authentication services, and the SSL Record Protocol (SSLRP), which packages the data for encryption. SSL provides greater security than HTTPS by encrypting all of the data passing between the client and the server, not just the HTTP data. Kerberos—Kerberos is an authentication protocol that directory services typically use to provide network users single logon capability. Microsoft’s Active Directory Services, for example, uses Kerberos authentication to control access to network resources. When a computer logs on to a network that uses Kerberos, a complex series of message exchanges takes place between the client, an authentication server, and the servers to which the client wants access. Because it uses a separate authentication server, Kerberos is known as a trusted third-party authentication protocol. These message exchanges are designed to authenticate the client to the servers without compromising network security by transmitting any sensitive data in clear text.

Objective 2.13

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Objective 2.13 Questions N10-002.02.13.001 Which of the following security protocols can make use of the encryption service IPsec’s ESP protocol provides? A. SSL B. PPTP C. Kerberos D. L2TP

N10-002.02.13.002 Which of the following protocols is designed to encrypt the application data transmitted over a LAN? A. IPsec B. SSL C. Kerberos D. L2TP

N10-002.02.13.003 Which of the following protocols tunnels data by encapsulating PPP frames in UDP datagrams? A. ESP B. PPTP C. L2TP D. SSL

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Correct Answers: D A. Incorrect: The SSL protocol does not use IPsec to encrypt data. B. Incorrect: The PPTP uses Rivest, Shamir, Adleman (RSA) RC4 encryption and does not require IPsec’s services. C. Incorrect: Kerberos encrypts only the data exchanged during the authentication process and does not use IPsec. D. Correct: The L2TP has no encryption capabilities of its own but uses the IPsec ESP protocol to protect the data passing through the tunnel.

N10-002.02.13.002

Correct Answers: A A. Correct: IPsec is one of the few security protocols that secures general LAN communications. B. Incorrect: SSL is designed to encrypt only the data Web servers and clients exchange. Web client/ server exchanges can take place on a LAN, but SSL is intended for the Internet. C. Incorrect: Kerberos is an authentication protocol that encrypts only the messages involved in the authentication process, not the application data that the computers transmit after the authentication is complete. D. Incorrect: L2TP is a tunneling protocol designed for virtual private network connections, not LANs.

N10-002.02.13.003

Correct Answers: C A. Incorrect: The ESP protocol encrypts data for transmission over a network, but it does not provide tunneling. B. Incorrect: The PPTP encapsulates PPP frames in IP datagrams, not UDP datagrams. C. Correct: The L2TP improves on the tunneling PPTP provides by encapsulating PPP frames inside UDP datagrams, after which the datagrams are usually encrypted using ESP. D. Incorrect: SSL provides data encryption to Web servers and clients, but it does not tunnel data.

O B J E C T I V E

D O M A I N

3

Network Implementation

Building a network starts with components such as computers, network interface adapters, cables, and hubs, but there are also many other hardware and software elements involved in network communications. To construct an efficient, useful, and secure network, you must also consider the characteristics of the client and server operating systems you plan to use, paying particular attention to their interoperability and security. There are also other technologies that you may or may not want to integrate into your network—technologies that can provide additional security, data storage, and network administration services.

Tested Skills and Suggested Practices The skills that you need to successfully master the Network Implementation objective domain on the Network+ Certification exam include:

Identifying the basic capabilities (i.e., client support, interoperability, authentication, file and print services, application support, and security) of the following server operating systems: UNIX/Linux, NetWare, Windows, and Macintosh. Practice 1: Examine the manufacturers’ Web sites for these operating systems and investigate the client connectivity options available for each one. Practice 2: On a lab network, install each of the server operating systems listed here on an appropriate computer and determine which one best fulfills your company’s or organization’s needs. Identifying the basic capabilities (i.e., client connectivity, local security mechanisms, and authentication) of the following clients: NetWare, UNIX/Linux, Windows, and Macintosh.

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Practice 1: On your lab network, configure a client workstation of each type to access the basic file and print services on as many of the servers as possible that you have available. Practice 2: Study the security capabilities of each of the clients listed here and determine which one, with an unlimited hardware and software budget, can conceivably provide the greatest amount of security. Identifying the main characteristics of virtual local area networks (VLANs). Practice 1: Make a list of functions or applications that can take advantage of a VLAN on a switched network. Practice 2: Draw a diagram of your network and select the computers that you would group into VLANs, using their functions as the criteria for including them in a VLAN instead of their physical locations. Identifying the main characteristics of network attached storage. Practice 1: Study the capabilities of the network attached storage (NAS) appliances in hardware catalogs or on Web sites and compare their features, including maximum storage capacity, RAID levels supported, network interface type, and price. Practice 2: Create a new design for your network in which all data is stored on NAS appliances instead of traditional servers. Determine how this change will affect the roles of the other servers on the network and decide whether NAS would be a cost-effective solution for your network. Identifying the purpose and characteristics of fault tolerance. Practice 1: Make a list of the various types of fault tolerance you can implement on a network. Practice 2: Create a new design for your network incorporating a redundant backbone. Identifying the purpose and characteristics of disaster recovery. Practice 1: Perform a standard full backup of a server on your lab network. Then, simulate a drive failure on the server by formatting its hard drive and see all that is involved in restoring the server to its original state without a specialized disaster recovery program. Practice 2: Obtain a trial version of a disaster recovery program from its manufacturer and implement it on your lab network. Then perform the same drive failure simulation, using the disaster recovery product to restore the drive.

Objective Domain 3

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Given a remote connectivity scenario (e.g., IP, IPX, dial-up, PPPoE, authentication, physical connectivity, etc.), configuring the connection. Practice 1: Create a diagram showing the steps involved in establishing a PPP connection between a remote client and a network server. Practice 2: Examine the controls used to configure a remote network connection in the client operating systems used on your network. Identifying the purpose, benefits, and characteristics of using a firewall. Practice 1: Make a list of the Internet applications most commonly used on your network and create a series of packet filtering scenarios that enable your users to continue their normal practices while protecting them from Internet intrusion. Practice 2: Create a diagram of a network that uses network address translation (NAT) to access the Internet, including the IP addresses of the workstations and the NAT server as well as a typical Internet client/server message exchange. Identifying the purpose, benefits, and characteristics of using a proxy server. Practice 1: Create a diagram of a network that uses a proxy server to access the Internet, including the IP addresses of the workstations and the proxy server as well as a typical Web client/server message exchange. Practice 2: Examine the configuration interface of the Web browsers you use on your network to see how you would configure them to use a proxy server. Given a scenario, predicting the impact of a particular security implementation on network functionality (e.g., blocking port numbers, encryption, etc.). Practice 1: Study the security products and techniques available for data networks and try to determine what noticeable effect (if any) they would have on your network. Practice 2: Perform a series of network-intensive tasks on your lab network using Windows 2000 clients and servers and note the exact time it takes you to accomplish them. Then activate Windows 2000’s IPsec feature on both the client and server computers and perform the same tasks again to see if there is a measurable difference in the elapsed times. Given a network configuration, selecting the appropriate NIC and network configuration settings (DHCP, DNS, WINS, protocols, NETBIOS/host name, etc.).

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Practice 1: Study the configuration interfaces of the client operating systems used on your network to see how you would select appropriate values for the parameters listed here. Practice 2: Study the functions of the services listed here and determine which are essential for network communications.


Objective 3.1 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 1 in Chapter 4, “Networking Software.” Microsoft Corporation. “Windows 2000 Interoperability Features.” This document is available at the Microsoft Web site at http://www.microsoft.com/windows2000/server/ evaluation/features/interop.asp. Microsoft Corporation. “Introduction to Interoperability: Using Windows 2000 in a Mixed Environment.” This document is available at the Microsoft Web site at http:// www.microsoft.com/windows2000/server/evaluation/business/interopsol.asp.

Objective 3.2 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 2 in Chapter 4, “Networking Software.” Microsoft Corporation. “Introduction to Interoperability: Using Windows 2000 in a Mixed Environment.” This document is available at the Microsoft Web site at http:// www.microsoft.com/windows2000/server/evaluation/business/interopsol.asp. Microsoft Corporation. Windows 2000 Server Resource Kit. Volume: Deployment Planning Guide. Redmond, Washington: Microsoft Press, 2000. Review Chapter 22, “Defining a Client Connectivity Strategy.”

Objective 3.3 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 2 in Chapter 3, “Network Connections.” Cisco Systems. “Overview of Routing Between Virtual LANs.” This document is available at the Cisco Systems Web site at http://www.cisco.com/univercd/cc/td/doc/ product/software/ios113ed/113ed_cr/switch_c/xcvlan.htm.

Objective Domain 3

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Objective 3.4 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 2 in Chapter 14, “Planning the Network.” Microsoft Corporation. “Storage Management Operations Guide.” February, 2001. This white paper is available at the Microsoft Web site at http://www.microsoft.com/ technet/treeview/default.asp?url=/TechNet/prodtechnol/windows2000serv/maintain/ opsguide/stormgog.asp.

Objective 3.5 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 2 in Chapter 14, “Planning the Network.” Russel, Charlie, and Sharon Crawford. Microsoft Windows 2000 Server Administrator’s Companion. Redmond, Washington: Microsoft Press, 2000. Review Chapter 35, “Planning Fault Tolerance and Avoidance.”

Objective 3.6 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 1 in Chapter 16, “Network Maintenance.” Microsoft Corporation. “Storage Management Operations Guide.” February, 2001. This white paper is available at the Microsoft Web site at http://www.microsoft.com/ technet/treeview/default.asp?url=/TechNet/prodtechnol/windows2000serv/maintain/ opsguide/stormgog.asp.

Objective 3.7 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 1 in Chapter 12, “Remote Network Access.” Microsoft Corporation. Windows 2000 Server Resource Kit. Volume: Internetworking Guide. Redmond, Washington: Microsoft Press, 2000. Review Chapter 7, “Remote Access Server.”

Objective 3.8 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 3 in Chapter 13, “Network Security.”

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Readiness Review—Exam N10-002 Microsoft Corporation. “Security Management for ASPs.” This white paper is available at the Microsoft Web site at http://www.microsoft.com/serviceproviders/whitepapers/ security_management_asps_p63310.asp.

Objective 3.9 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 3 in Chapter 13, “Network Security.” Microsoft Corporation. “Deploying Secure Windows 2000-based Firewalls and Remote Access.” This white paper is available at the Microsoft Web site at http:// www.microsoft.com/technet/treeview/default.asp?url=/TechNet/prodtechnol/ windows2000serv/deploy/mspraswp.asp. Microsoft Corporation. Windows 2000 Server Resource Kit. Volume: Internet Explorer 5 Resource Guide. Redmond, Washington: Microsoft Press, 2000. Review Chapter 21, “Using Automatic Configuration and Automatic Proxy.”

Objective 3.10 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lessons 3 and 4 in Chapter 13, “Network Security.” Microsoft Corporation. “Security Administration Operations Guide.” This white paper is available at the Microsoft Web site at http://www.microsoft.com/technet/treeview/ default.asp?url=/TechNet/prodtechnol/windows2000serv/maintain/opsguide/ secadmog.asp.

Objective 3.11 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 2 in Chapter 11, “TCP/IP Configuration.” Microsoft Windows 2000 Server Documentation. Link directly to the Windows 2000 Server Documentation page at http://www.microsoft.com/windows2000/en/server/help/ sag_TCPIPtopnode.htm?id=1768. Microsoft Windows 2000 Server Documentation. Link directly to the Windows 2000 Server Documentation page at http://www.microsoft.com/windows2000/en/server/ help/. “Networking” is listed on the left with “TCP/IP” listed one level below. Microsoft Corporation. Windows 2000 Server Manual. Redmond, Washington: Microsoft Corporation, 2000. Review the section titled “Networking: TCP/IP.”

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3 . 1

Identify the basic capabilities (i.e., client support, interoperability, authentication, file and print services, application support, and security) of the following server operating systems: UNIX/Linux, NetWare, Windows, Macintosh.

Virtually all of the operating systems used today have networking capabilities built into them. At the very least, the systems can recognize and use a network interface card installed in the computer and also includes support for the most common protocols used in networking, such as TCP/IP. Most operating systems also include other networking features, such as file and printer sharing and Internet clients and servers. In the early days of computer networking, clients’ and servers’ roles were more strictly segregated than they are now. Most of today’s operating systems use the peer-to-peer networking model. A peer-to-peer operating system is capable of functioning as both a client and a server, meaning that it can access resources shared by other computers as well as share its own resources. The main exception to this is Novell NetWare, which has always been strictly a client/server operating system. Despite the fact that client and server capabilities are built into most operating systems, it is still common for networks to dedicate computers to the server role. The most common operating systems have varying degrees of server capability, as follows:

UNIX/Linux—The many variants of the UNIX and Linux operating systems differ greatly in the applications they include, but they are all based on the same TCP/IP networking protocols. All UNIX/Linux computers have support for the basic TCP/ IP applications, such as FTP and Telnet clients and servers. These applications enable UNIX/Linux computers of any type to communicate with each other over a network and with any other operating system that supports TCP/IP. UNIX and

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Readiness Review—Exam N10-002 Linux are better suited to the role of application server than file and print server. While FTP and Telnet provide file and remote terminal access to TCP/IP clients of all types, they do not provide file and printer sharing in the traditional sense. Many of the UNIX/Linux operating systems support Network File System (NFS) file sharing, which enables a computer to mount another computer’s drives into its own file system. Other operating systems, such as Windows 2000/NT and NetWare, can also support NFS with the use of add-on software products. The line printer daemon (lpd) and line printer remote (lpr) programs provide printer sharing among UNIX/Linux and other computers. Security in UNIX and Linux is not as standardized, however. TCP/IP applications such as FTP and Telnet use clear text passwords that are not very secure, although some operating systems include directory services and support for access control lists that provide greater security.

Novell NetWare—NetWare is a server operating system only, which has no client capabilities. The client computers run other operating systems, with a NetWare client application installed. On a pure NetWare network, the clients cannot communicate with each other, only with the NetWare servers. Until NetWare version 5, the operating system did not include native support for the TCP/IP protocols; clients had to run the Novell IPX protocols to access NetWare file and print services. The NetWare product includes clients for the various Windows operating systems; UNIX/Linux and Macintosh connectivity are provided by add-on products. NetWare is best known as a file and print server; its support for server applications is relatively limited when compared to Windows and UNIX/Linux. For authentication and security, NetWare relies on Novell Directory Services (NDS), which is an enterprise directory service that runs on a variety of computing platforms. Microsoft Windows 2000/NT Server—Windows 2000 Server and Windows NT Server are the Windows versions intended for server use. The 2000 Professional and NT Workstation products can also perform basic server tasks, such as file and printer sharing. Windows 2000 and NT can support clients running any version of DOS or Windows using the TCP/IP, IPX, or NetBEUI protocols, and products such as Microsoft Services for Macintosh and Microsoft Services for UNIX provide client connectivity for other platforms. Windows 2000 and NT are designed to be allpurpose server products. NetWare may be a better file and print server platform than Windows, and UNIX may be a better application server, but neither of these operating systems performs the other function as well as Windows does. Active Directory service included with Windows 2000 provides single network logon and better security overall than Windows NT domains. Apple Macintosh—Macintosh computers are used as servers primarily on allMacintosh networks. While it is now possible to run standard protocols such as TCP/IP on Macintosh networks (rather than the proprietary AppleTalk protocols) and to provide basic file and printer sharing services to other operating systems, network application support on the Macintosh platform is limited and the security is rudimentary.

Objective 3.1

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Objective 3.1 Questions N10-002.03.01.001 Which of the following operating systems is capable of functioning as a server, but not as a client? A. Linux B. NetWare C. Microsoft Windows 2000 Server D. Macintosh operating system

N10-002.03.01.002 You are the new administrator of a 12-node peer-to-peer network that is about to add its first server. The workstations are mostly PCs running Windows 98 and Windows 2000 Professional, but the network also has a few Macintosh and UNIX computers. What is the best operating system to run on the server and why? A. UNIX, because UNIX is the easiest operating system to set up for file and printer sharing with Windows and Macintosh clients. B. NetWare, because it includes Windows, Macintosh, and UNIX client software in the package. C. Windows 2000 Server, because it provides native support for all Windows clients and can support Macintosh and UNIX clients with add-on products. D. Macintosh, because all of the networking hardware and software you need is supplied with the computer.

N10-002.03.01.003 Which of the following operating systems does not include native support for TCP/IP? A. Windows 2000 B. Macintosh C. UNIX D. NetWare 4.11

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N10-002.03.01.004 Which of the following statements about file and printer sharing for particular server operating systems is true? (Choose two.) A. All UNIX and Linux operating systems provide transparent file and printer sharing for all of the major client platforms. B. Microsoft Windows 2000 and NetWare servers can share files and printers with clients running any version of Windows without using software not included with the operating system. C. It is impossible to share a printer connected to a Macintosh server with any computer not running the Macintosh operating system. D. Windows 2000 provides more secure file and printer sharing than Windows NT.


Correct Answers: B A. Incorrect: All Linux (and other UNIX) operating systems can function as both servers and clients. B. Correct: NetWare servers run a proprietary operating system that has no client capabilities. C. Incorrect: Windows 2000 Server differs from Windows 2000 Professional mainly in the additional server applications it provides, but the client capabilities are the same in both operating systems. D. Incorrect: All Macintosh computers have the same networking support, which includes client capabilities.

N10-002.03.01.002

Correct Answers: C A. Incorrect: Configuring a UNIX computer to support Windows and Macintosh clients is possible, using applications such as NFS and lpd, but special software is required on both the client and server computers and the process is far from easy. B. Incorrect: NetWare includes clients that support DOS and all of the Windows operating systems. Macintosh and UNIX client support is not included in the NetWare package, but it is available using Novell add-on products.

Objective 3.1

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C. Correct: Windows 2000 can support clients running any version of DOS or Windows, and Microsoft Services for UNIX and Services for Macintosh provide connectivity for the other clients on the network. D. Incorrect: While Macintosh computers do have a network interface and networking software as standard equipment, this hardware and software is designed primarily to connect Macintosh computers together, not to build a heterogeneous network. Of the four choices listed here, Macintosh is the operating system least suitable for use as a cross-platform server.

N10-002.03.01.003

Correct Answers: D A. Incorrect: Windows 2000 uses TCP/IP as its default networking protocols. B. Incorrect: Although the networking capability originally included with Macintosh computers used the proprietary AppleTalk protocols, all Macintoshs now support TCP/IP. C. Incorrect: The UNIX operating systems were designed around the TCP/IP protocols; all UNIX and Linux variants use them. D. Correct: NetWare version 5 was the first version of the operating system to include TCP/IP support for its native file and print functions. Clients must use the IPX protocols to access file and print services on a NetWare 4.11 server.

N10-002.03.01.004

Correct Answers: B and D A. Incorrect: Many UNIX and Linux operating systems include applications such as NFS and lpd, which can provide file and printer sharing services for other platforms, but not all of them do. B. Correct: Any of the Windows network operating systems can share files and printers with any other Windows operating system. NetWare includes client software for all Windows versions that enables them to access NetWare files and printers. C. Incorrect: It may not be as easy as it is with other operating systems, but Macintosh servers can provide file and print services to other platforms. D. Correct: Windows 2000 includes Active Directory directory services, which provides third-party authentication using the Kerberos protocol. This is an improvement over the security included in Windows NT.


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3 . 2

Identify the basic capabilities (i.e., client connectivity, local security mechanisms, and authentication) of the following clients: NetWare, UNIX/Linux, Windows, Macintosh.

A client is simply a software component that can access the resources shared by a server. In some cases, a client is an application that is designed to communicate with a server application on another computer, while in other cases, the client capabilities are built into the operating system. In the latter case, the primary function of the operating system client is to access the file and print services the server provides. Most of the operating systems that you can use for server computers can also function as clients, although cross-platform connectivity can be tricky at times. The primary clients used on today’s LANs are as follows.

NetWare—NetWare is unusual because it does not include a client operating system of its own. NetWare is a server operating system, and it includes client software packages for the operating systems most commonly used as workstations, including MS-DOS, Windows 3.1, Windows 95 and 98, and Windows NT and 2000. This client software augments the existing networking capabilities built into the Windows operating systems to provide NetWare connectivity in addition to the existing Windows connectivity. Note, however, that Windows 95 and 98, and Windows NT and 2000, also include their own NetWare clients that Microsoft created. The Novell clients provide the same basic functions as the Microsoft clients, plus additional features such as the capability to run the NetWare Administrator application. The Novell clients enable the computer to log in to the NetWare network using NDS, which can provide users with access to NetWare (and other) resources all over the network. Connecting computers running operating systems other than Windows to NetWare servers is more problematic. Both UNIX/Linux and Macintosh clients require installation of additional software, either on the client or the server.

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UNIX/Linux—All UNIX and Linux operating systems contain the standard TCP/ IP client applications, such as FTP and Telnet. In addition, Web browsers for virtually all of the UNIX/Linux operating systems are readily available. However, UNIX/Linux cannot access the file and print services that Windows, NetWare, or Macintosh servers provide without special arrangements. UNIX systems typically use the NFS to access the drives in other computers and the lpr program to access shared printers. However, Windows, NetWare, and Macintosh do not use these services by default, although you can add them in some cases by purchasing additional software. The security mechanisms included with UNIX and Linux vary with the different operating systems. Microsoft Windows—All of the Windows operating systems, with the exception of Windows 3.1, include client software that enables the computer to access both Windows and NetWare resources. The Microsoft clients for NetWare included with the operating systems provide NDS login capability, basic NetWare file and print connectivity, and generally better performance than the Novell clients, but you can’t use them to run the NetWare Administrator program or other NDS utilities. To access file and print services on UNIX and Linux servers with Windows, you must use NFS and lpr, just as you do to access Windows servers with UNIX/Linux. Windows 2000 and NT include the lpr program, and the Microsoft Services for UNIX product provides NFS client as well as server capabilities. Windows provides its own local security mechanisms, in addition to Active Directory, with Windows 2000 server. Windows 95 and 98 provide share-based security, in which resources are protected with a common password all users employ. Windows NT and 2000 include their own local security accounts manager (SAM), which makes it possible to create local accounts for individual users. Apple Macintosh—Macintosh computers can, of course, function as clients of Macintosh servers, and they can also be made to connect to other server operating systems. However, in nearly all cases, you make the modifications needed to provide this cross-platform connectivity to the server and not to the client. Microsoft Services for Macintosh, included with Windows NT and 2000 but not installed by default, enables the Windows computer to provide file, print, and authentication services to Macintosh clients using either the AppleTalk or TCP/IP protocols. NetWare servers include support for the AppleTalk protocols, and a product called Novell Native File Access for Macintosh enables NetWare servers to support Macintosh clients using TCP/IP. There is also a Novell Client for MacOS, which is the only Macintosh client solution for NetWare that you actually install on the client computer. Macintosh clients include the standard TCP/IP client programs, such as FTP and Telnet, which enable them to connect to the equivalent server applications on UNIX and Linux computers. However, for Macintosh clients to access files on a UNIX or Linux server, a third-party NFS solution for the Macintosh computers is required.

Objective 3.2

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Objective 3.2 Questions N10-002.03.02.001 Windows 2000 includes file and print client support for which of the operating systems (without purchasing additional software)? A. Windows NT and 2000 only. B. Windows 95 and 98, and Windows NT and 2000. C. Windows 95 and 98, and Windows NT and 2000, plus NetWare. D. Windows 95 and 98, and Windows NT and 2000, plus NetWare, UNIX, and Linux.

N10-002.03.02.002 As the new administrator of a TCP/IP-only network running Windows 2000 servers and mixed Windows clients, you must install new Macintosh workstations and connect them to the network. The Macintoshes must be able to store their data files and use the printers on network servers. The previous administrator had planned to install a Macintosh server on the network specifically for the Macintosh workstations to use. Which of the following courses of action would you choose? A. Cancel the project because Macintosh computers support only peer-to-peer networking with other Macintoshes, and not client/server networking with other operating systems. B. Proceed with the previous administrator’s plan because a Macintosh server is the only way to service Macintosh clients. C. Do nothing because the Windows 2000 servers support Macintosh clients already. D. Install Microsoft Services for Macintosh on one of the Windows 2000 servers, which enables Windows 2000 to provide file and print services to Macintosh clients.

N10-002.03.02.003 What advantages are there to running a Novell client for NetWare on a Windows computer instead of the Microsoft client for NetWare? A. The Novell client provides NDS login capabilities and the Microsoft client does not. B. The Novell client enables users to access NetWare printers and the Microsoft client provides only file system access. C. The Novell client provides better performance than the Microsoft client. D. The Novell client enables users to run NetWare Administrator (NWAdmin) and other NDS applications and the Microsoft client does not.

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Correct Answers: C A. Incorrect: Windows 2000 computers can connect to any Windows server computer as a client, not just other Windows 2000 and Windows NT systems. B. Incorrect: Windows 2000 computers can indeed connect to any Windows 95 and 98 or Windows NT and 2000 system as a client, but the operating system also includes a NetWare client. C. Correct: Windows 2000 includes client support for all Windows operating systems and for NetWare. D. Incorrect: Windows 2000 does include file and print client support for all Windows versions and for NetWare, but it cannot connect to UNIX or Linux servers without additional software.

N10-002.03.02.002

Correct Answers: D A. Incorrect: There is no need to cancel the project because while connecting Macintosh clients to servers running other operating systems may require additional software, it is by no means impossible. B. Incorrect: Installing a Macintosh server is one possible solution, but it is not the only one, and it certainly is not the most practical one in this case. Since there are already Windows 2000 servers on the network, a solution that provides Macintosh client access to Windows is preferable. C. Incorrect: Windows 2000 includes Services for Macintosh, which provides Macintosh client support but does not install it by default. D. Correct: Microsoft Services for Macintosh enables Macintosh clients to store files on a Windows 2000 server, using either the AppleTalk or TCP/IP protocols, and to access Windows 2000 printers.

N10-002.03.02.003

Correct Answers: D A. Incorrect: Both the Microsoft and Novell clients for Windows provide the capability to log in to an NDS tree and access NetWare resources throughout the network. B. Incorrect: The Microsoft and Novell clients both provide access to NetWare files and printers. C. Incorrect: Performance of the Novell client for Windows, in terms of access speed, is generally worse than that of the Microsoft client. D. Correct: The NetWare Administrator application enables network support personnel to view, create, and modify objects in the NDS database. The Novell client for Windows includes the support files that enable users to run NetWare Administrator and the Microsoft client does not.

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3 . 3

Identify the main characteristics of VLANs.

Many private internetworks are being constructed using switches in places where routers would formerly have been used. While routers connect local area networks (LANs) at the network layer, switches create data-link layer connections, essentially turning an internetwork into one big LAN. Because a switch forwards incoming traffic only to the computer for which it is destined, each pair of computers has what amounts to a dedicated connection between them using the full bandwidth of the network medium. The number of collisions on the network does not increase, and overall efficiency improves. When you use switches instead of routers, however, you remove the natural administrative boundaries that individual LANs provide. A broadcast transmission generated by one computer, for example, instead of being limited to a relatively small LAN, is unnecessarily propagated by the switches throughout the entire network. To address this problem, create virtual LANs (VLANs) on a switched network. A VLAN is a group of computers or other network devices that function as an individual subnet. A broadcast transmission generated by one of the systems in a VLAN is propagated by the switches only to the other systems in the VLAN, instead of to the entire network. To create a VLAN, select devices by specifying their hardware addresses, switch port numbers, or in some cases, IP addresses. VLANs are independent of the network’s physical configuration. The systems in a particular VLAN can be located anywhere on the network regardless of their proximity to the other systems. VLANs exist as an overlay on top of the data-link layer switching fabric. All of the computers are connected using switches, but for communications between VLANs routers are needed, just as with physically configured subnets. There are two basic techniques for mixing the switching and routing functions in a VLAN environment. One is known as “switch where you can, route where you must” and is intended for networks on which most of the traffic is between devices in the same VLAN. In this method, all of the intra-VLAN traffic is switched and all traffic between VLANs is routed. In this case, the switches must have a port that connects them to a router. The second technique, intended for networks in which most of the traffic is generated by inter-VLAN communications, uses routers to establish connections between systems on different VLANs and then uses switching once the connection is in place, thus minimizing routing delays. This technique, known as “route once and switch afterward,” goes by other names, such as layer 3 switching, multilayer routing, and cutthrough routing, and is typically implemented in combination router/switch devices.

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Objective 3.3 Questions N10-002.03.03.001 Which of the following devices is used to physically connect computers in the same VLAN? A. A bridge B. A hub C. A switch D. A router

N10-002.03.03.002 VLANs create the administrative boundaries on a switched network that are usually provided by which of the following devices? A. Hubs B. Routers C. Domains D. Bridges

N10-002.03.03.003 Which of the following statements about VLANs are true? (Choose two.) A. All of the devices in a particular VLAN must be physically connected to the same switch. B. A VLAN creates a limited broadcast domain on a switched network. C. You must have VLANs on a switched network for communication between computers on different cable segments to occur. D. A router is required for communication between VLANs.

N10-002.03.03.004 Which of the following can be used to identify the devices in a particular VLAN? (Choose three.) A. Hardware addresses B. IP addresses C. DNS names D. Switch port numbers

Objective 3.3

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Correct Answers: C A. Incorrect: Bridges connect network segments at the data-link layer and they also selectively forward traffic between the segments. However, bridges do not provide a dedicated connection between two systems like a switch does and they do not make it possible to convert a large routed internetwork into a single switched network. Therefore, they have no role in implementing VLANs. B. Incorrect: Hubs are physical layer devices that propagate all incoming traffic out through all of their ports. Replacing the routers on an internetwork with hubs would create a single network with huge amounts of traffic and collisions. Hubs, therefore, do not connect the computers in a VLAN. C. Correct: Replacing routers with switches turns an internetwork into a single large LAN, and VLANs exist as logical elements on top of the switching fabric. D. Incorrect: Although VLANs are the functional equivalent of network layer subnets, the systems in a single VLAN are still connected by switches, not routers.

N10-002.03.03.002

Correct Answers: B A. Incorrect: Because hubs propagate all of the traffic they receive out through all of their ports indiscriminately, they create no administrative boundaries. B. Correct: Connecting LANs with routers at the network layer maintains the data-link layer administrative boundaries that prevent broadcast transmissions from being propagated throughout the entire internetwork. Switching eliminates those data-link layer boundaries, and VLANs are required to simulate them. C. Incorrect: Domains are logical groups of network devices defined by the Domain Name System (DNS) or a directory service. Their functions are not related to VLANs in any way. D. Incorrect: Switches are essentially multiport bridges that forward incoming traffic only to the device for which it is destined. Therefore, bridges are more closely related to eliminating administrative boundaries than to establishing them.

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N10-002.03.03.003

Correct Answers: B and D A. Incorrect: The computers in a single VLAN can be located anywhere on a switched network irrespective of the switches’ physical configuration. B. Correct: A broadcast message generated by a computer in a VLAN is transmitted to all of the other computers in that VLAN only, just as if the systems were physically located on a separate LAN or subnet. C. Incorrect: Unicast transmissions between computers on a switched network do not require VLANs because the switches create what amounts to a direct connection between the two systems. VLANs are needed only for communication processes that require using broadcasts, which if transmitted without VLANs would flood the network. D. Correct: Even though they are a purely logical construction, VLANs function just like physical LANs or subnets and require routers for communication between them. Routers are integrated with switches on the network to enable inter-VLAN communication.

N10-002.03.03.004

Correct Answers: A, B, and D A. Correct: Every network device has unique hardware addresses coded into the network interface adapter, and administrators can use these addresses to select the devices that will be part of a specific VLAN. B. Correct: In layer 3 switching, where the routing and switching functions are combined into a single hardware device, it’s possible to identify the computers in a VLAN using their network layer IP addresses. C. Incorrect: Although they do uniquely identify computers on a network, DNS is an application layer process and has nothing to do with the switching and routing process, which occur at the data-link layer. Therefore, you cannot use DNS names to identify the computers in a VLAN. D. Correct: When VLANs are implemented inside the switch, selecting the ports to which specific computers are attached is a simple way to identify the computers in a particular VLAN.

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3 . 4

Identify the main characteristics of network attached storage.

The increasing popularity of network storage technologies such as Redundant Array of Independent Disks (RAID) has led to the introduction of specialized drive arrays designed to support the technology. Many network server computers now come equipped with an integrated RAID array that the owner can populate with disk drives as needed. When large amounts of storage and fault tolerance are needed, drive arrays in the form of separate hardware devices are also popular. These external arrays have their own power supplies and often can support many more drives than an internal array. At first, external drive arrays were standard SCSI (Small Computer System Interface) devices that you could connect to a SCSI host adapter in a server with an external connector. As these arrays became more popular, however, the next logical step in their development was to connect them directly to the network. This concept provides a number of advantages, such as the array’s ability to take advantage of today’s highspeed LAN technologies and the capability of multiple devices on the network to access the array. By not permanently associating the array with any one server, you create an additional level of fault tolerance. In the event of a server failure, a backup server can take over by accessing the same data in the array. There is no need to perform a restoration from a backup tape or to maintain a redundant drive array. The RAID arrays themselves are not totally immune from failure. For this to be possible, however, the drive array has to have a network interface adapter, just like a computer, and a processor and software that enable the array to use the network interface for communications with other network devices. The result is a technology called network attached storage (NAS), which takes the form of a self-contained drive array, often called a NAS appliance. The NAS appliance is a file server—a special purpose computer that not only contains a drive array and a network interface adapter but also a proprietary operating system that is optimized for storage input/output (I/O) tasks. The NAS appliance contains its own file system that makes the stored data directly available to the other computers on the network using a standardized file system protocol, such as the NFS or the Common Internet File System (CIFS).

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Readiness Review—Exam N10-002 You can deploy a NAS appliance in two basic ways. By connecting the appliance directly to your network, all of your computers can directly access the files stored there. This means that clients and servers can access the appliance like any other file server on the network. This reduces the burden on your existing servers, but it can also increase the amount of traffic on the network. If, for example, you use a NAS appliance to store a large database, the database application server has to access the files on the NAS appliance over the network and them transmit them to the database clients. This entire process doubles the traffic that storing the database files on the application server would generate. The second method for deploying NAS appliances is to create a dedicated network called a storage area network (SAN). A SAN is a separate network that is devoted to storage I/O traffic. The SAN connects your servers to NAS appliances and other storage-related devices, such as disk arrays and backup drives. The servers access data from the devices on the SAN and furnish it to network clients over the separate user network. This arrangement makes the data available to all of your servers without flooding the user network with I/O traffic. If a server fails, then another one connected to the SAN can take over its functions using the same data source. A SAN can use any network technology that provides sufficient bandwidth to handle the I/O traffic, but they are most commonly associated with a protocol called Fibre Channel, which uses fiber optic cable to transfer data at up to 200 MBps.

Objective 3.4

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Objective 3.4 Questions N10-002.03.04.001 Which of the following components is typically not a part of a NAS appliance? A. A network interface adapter B. A hard drive array C. A SCSI interface D. An application server

N10-002.03.04.002 Which of the following components does a NAS appliance have that a standalone RAID array does not? (Choose two.) A. A SCSI interface B. An operating system C. A hard disk drive array D. A network interface adapter

N10-002.03.04.003 Which computers can access a NAS appliance that is connected to a standard Ethernet-user LAN? A. Any computer on the network B. Only the server computers on the network C. Only the client workstations on the network D. Only one specific computer that is specifically configured to access the appliance

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N10-002.03.04.004 Your company is deploying a new Web-based order entry application that is vital to its continued existence. Any time that the application is down means lost orders and lost revenue. You have engaged four network contractors to submit bids on a storage solution for the application. The primary objective of the solution is to provide fault tolerance that will keep the order entry data available and the application running around the clock. The secondary solutions are to minimize the effect of the new storage solution on the existing user network and to create regular backups of the company data that can be stored offsite. Of course, economy is always a factor, and you want to satisfy your objectives with as little expenditure as possible. The three contractors’ proposals are as follows:

The first contractor proposes the installation of a NAS appliance on the existing network along with redundant servers running the Web application. The second contractor proposes the installation of a standalone RAID array for storing the order entry data and a tape drive, which are both to be connected to the Web server running the application. The third contractor proposes the installation of a separate SAN connecting two redundant Web servers, one equipped with a tape drive, to a NAS appliance. The fourth contractor proposes the installation of a dedicated server on the existing network containing a state-of-the-art digital linear tape (DLT) autochanger, on which a copy of the company’s data will be stored. Which of the four contractors comes closest to satisfying the objectives without over-spending? A. The first contractor B. The second contractor C. The third contractor D. The fourth contractor

Objective 3.4

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Correct Answers: D A. Incorrect: A NAS appliance connects directly to a network and therefore must have a network interface adapter of some sort either integrated or installed into it. B. Incorrect: A NAS appliance’s storage capacity is provided by a drive array that is fundamentally the same as those used in computers and external storage arrays that you connect directly to a computer. C. Incorrect: Although a NAS appliance does not use SCSI to connect to a computer, as earlier types of external drive arrays do, the drive array uses SCSI internally to connect the drives to the rest of the system. D. Correct: A NAS appliance is a dedicated file server and does not run the applications that actually use the data stored on it. The applications run on a separate server and access the data over a network connection.

N10-002.03.04.002

Correct Answers: B and D A. Incorrect: A NAS appliance’s core technology is a drive array, just like that of a standalone RAID array. Even though the NAS appliance does not connect directly to the SCSI bus of a server, it must still have a SCSI interface for the drives to communicate among themselves and with the operating system. The standalone array uses SCSI for communication between the drives in the array and with the host computer. B. Correct: A NAS appliance is essentially a computer devoted to file service tasks, and therefore it has an operating system to manage the array and provide file system services to network clients. The operating system is usually not the same as the off-the-shelf products used on most computers; it is stripped down and dedicated to the specific tasks it must perform. A standalone RAID array must be connected to a computer and uses its operating system for these purposes because it has no operating system of its own. C. Incorrect: An array of hard disk drives is the functional core of both the NAS appliance and the standalone RAID array. Both store data in the same way and differ only in their capability to use the stored data. D. Correct: A NAS appliance connects to either a standard user network or to a dedicated SAN. Therefore, the appliance must have a network interface adapter. A standalone RAID array connects directly to a computer using SCSI and so does not require a standard network interface adapter.

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N10-002.03.04.003

Correct Answers: A A. Correct: A NAS appliance is a fully functional, self-contained file server, so connecting a NAS appliance to a user LAN enables any computer on the network to access its services. B. Incorrect: When you connect a NAS appliance to a user network, any computer can access its services. It is not necessary for a separate server to access files from the appliance and then serve them to clients—the clients can access them directly. The only instance in which a separate server is needed is when it is necessary to run an application (such as a database manager) that processes the data before furnishing it to clients. C. Incorrect: Both server and client computers can access the files stored on a NAS appliance as long as they have the appropriate software to support the network file system that the appliance uses. D. Incorrect: The chief benefit of a NAS appliance is that is connected to a network using a standard interface, so multiple computers can access it at the same time. If, for example, you store your company database on a NAS appliance and your database server malfunctions, you can bring up a redundant server to function in its stead, using the same data stored on the appliance.

N10-002.03.04.004

Correct Answers: C A. Incorrect: Connecting the NAS appliance to the existing network along with redundant Web servers provides the necessary fault tolerance because either one of the servers can access the order entry data stored on the appliance. However, this solution does not satisfy all of the objectives because there is no backup solution, and adding the NAS appliance to the existing network will result in a marked increase in traffic levels. B. Incorrect: The RAID array provides fault tolerance in the event of a drive failure and the tape drive provides a backup solution, but this proposal places all of the new equipment into a single server. If that server suffers a catastrophic failure, the application would be offline for a significant length of time until a new server is prepared and the data restored to it from tape. C. Correct: Building a separate SAN isolates the Web servers and the NAS appliance from the user network, preventing it from being flooded with I/O traffic while providing complete fault tolerance in the event of a drive or server failure. The tape drive in one of the servers provides a backup solution for offsite storage. D. Incorrect: A dedicated backup server can protect the order entry data from loss in the event of a disaster, but the process of restoring the data from tape can be a lengthy one, and the application would not be running all during this time.

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3 . 5

Identify the purpose and characteristics of fault tolerance.

Fault tolerance is a system’s capability to continue providing its services after a malfunction. In most cases, you make a system fault tolerant by adding redundant components, so if one fails, another can take over its role. The best type of fault tolerance is when the redundant components are designed to automatically take over for their counterparts in the event of a failure, with no human intervention. Then it is not necessary to have people present to continuously monitor the system. One of the most likely components in a computer to fail, and the one that is most commonly duplicated in fault tolerant systems, is the hard disk drive. Backup devices, such as tape drives, can protect the data stored in a computer by making regular copies, but the process of restoring data from tape or other backup media can be lengthy and can occur only after a malfunctioning drive has been repaired or replaced. Backups are a form of fault tolerance, but they aren’t sufficient for a mission critical system that must run continuously. This is why many network servers use redundant hard disk drives in addition to a backup solution. The simplest form of hard drive redundancy is disk mirroring (RAID level 1), in which two identical hard drives connected to a single host adapter maintain duplicate copies of all of the stored data. When an application saves data to a file, the host adapter automatically writes it to both drives at the same time. If one of the drives fails, the other continues working normally until it can be replaced. Disk duplexing is a variation on the mirroring arrangement in which the system uses duplicate host adapters as well as duplicate drives. This enables the computer to continue operating if either an adapter or a drive fails, along with providing increased performance. Most server operating systems, including Microsoft Windows 2000 and NetWare, support disk mirroring and duplexing with no special hardware other than the redundant drives and/or controllers. Hardware RAID solutions are much more robust and reliable than those of software-based solutions included with some operating systems. The advantages of disk mirroring and duplexing are the immediate failover capability that the redundant equipment provides and an increase in disk read performance, because the read requests can be split among the two drives. The disadvantages are that

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Readiness Review—Exam N10-002 write performance is degraded because of writing the same data to two different drives, so you realize only half of the usable disk space you’ve paid for. Disk duplexing provides better read and write performance by splitting the data between the controllers. RAID is a technology that takes the mirroring/duplexing concept further by using multiple hard disk drives in a variety of configurations, called RAID levels, to provide fault tolerance with greater efficiency. RAID level 0 uses a technique called disk striping to split files into small segments and store them one by one on different drives in the array. Disk striping does not provide fault tolerance, but it does improve performance by splitting read and write requests among different drives in the array, minimizing the latency the drive head movements generate. RAID level 1 is disk mirroring. Many of the other RAID levels combine these two techniques to provide fault tolerance without the performance degradation of standard mirroring/duplexing and while maximizing the amount of storage space the array provides. The most popular of these advanced RAID technologies is RAID level 5, which stripes data plus a type of error correcting code (ECC) called parity across three or more hard disk drives. The parity information enables the array to reconstruct the data on any one of the drives if it fails. Because all of the data is not exactly duplicated, as in disk mirroring, a RAID 5 array realizes more storage capacity than mirrored or duplexed drives. Other RAID levels offer variations on RAID 5 that provide even greater fault tolerance, such as RAID 6, which maintains two complete copies of the parity information, but comes at a higher performance cost. RAID 5 continues to operate until two physical drives fail, while RAID 6 continues until three drives fail. Fault tolerance is not limited to hard drives, however. Other components in a computer can have redundant duplicates, such as fans and power supplies. It’s also possible to deploy multiple computers as redundant servers, so if any hardware or software component in one server malfunctions, there is a complete, operational duplicate ready to take over its role. A group of two or more redundant computers with software installed that provides near-instantaneous failover capability is called a cluster. Computers in a cluster can also share the work load that a single application generates. For example, for a highly-trafficked Web site, you can deploy a cluster of Web servers, known as nodes, each of which handles part of the client traffic. If one server fails, the others take up the slack, and as traffic to the site increases, the administrators have only to connect additional servers to the cluster. The number of nodes that you can add to a cluster is dependent on the operating system. You can also build fault tolerance into the design of your network by using elements such as redundant backbones. A backbone network connects multiple LANs to form an internetwork. Each LAN is connected to the backbone by a router. If one of the backbone routers fails, its LAN is isolated from the rest of the internetwork. By constructing a second backbone network and using two routers for every LAN, you create an internetwork that can tolerate a router failure and still function properly. You can also use the redundant backbone to balance the internetwork traffic load the LANs generate.

Objective 3.5

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Objective 3.5 Questions N10-002.03.05.001 Which of the following storage technologies does not provide fault tolerance? A. Disk mirroring B. Disk duplexing C. Disk striping D. Disk striping with parity (RAID 5)

N10-002.03.05.002 Which of the following terms describes a disk array with two drives containing identical data connected to a single host adapter? A. Disk duplexing B. Disk mirroring C. Disk striping D. Disk parity

N10-002.03.05.003 Which of the following storage technologies provides the greatest amount of usable disk space per megabyte of physical disk space? A. Disk striping B. Disk duplexing C. Disk mirroring D. RAID 5

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N10-002.03.05.004 How does a drive array using RAID 5 provide fault tolerance? A. By dedicating one of the drives in the array to storing parity data B. By mirroring each of the drives in the array C. By storing a duplicate copy of each stripe on another drive D. By striping parity information along with the data

N10-002.03.05.005 Which of the following fault tolerance technologies enables a network to continue operating normally after a router failure? A. A RAID array B. A redundant backbone C. A server cluster D. ECC


Correct Answers: C A. Incorrect: Disk mirroring provides fault tolerance by using identical disk drives containing duplicate data that are connected to a single host adapter. The system can continue to operate even if one drive fails. B. Incorrect: Disk duplexing provides fault tolerance in the same manner as disk mirroring, except that each drive is connected to a separate host adapter. C. Correct: Disk striping stores files on multiple drives by splitting them into blocks and writing each block to a different drive in round-robin fashion. This technique improves disk performance, but it does not provide fault tolerance. D. Incorrect: A RAID 5 array provides fault tolerance by generating parity information for the data it stores and striping both the parity and the data on multiple drives.

Objective 3.5

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N10-002.03.05.002

Correct Answers: B A. Incorrect: Disk duplexing uses two drives containing identical data, but each drive is connected to a separate host adapter. B. Correct: Disk mirroring uses two drives connected to one host adapter to store identical copies of all the stored data files. C. Incorrect: Disk striping can conceivably use two drives connected to a single host adapter, but the drives do not contain identical data because striping does not provide fault tolerance. D. Incorrect: Parity is the term given to the ECC that RAID arrays use to reconstruct lost data. Disk parity does not describe a specific hardware configuration.

N10-002.03.05.003

Correct Answers: A A. Correct: Disk striping does not provide fault tolerance because it does not create redundant copies of any of the stored data. Therefore, none of the storage space on the drive array is wasted, enabling it to store more data than fault tolerant solutions. B. Incorrect: Disk duplexing calls for using two drives to store identical copies of all files written to the array. As a result, the array realizes only half of its nominal capacity as usable disk space. C. Incorrect: Disk mirroring operates on the same principle as disk duplexing, except it uses a single host adapter. Therefore, a mirrored drive array provides the same amount of disk space as a duplexed array, which is half of its nominal capacity. D. Incorrect: A RAID 5 array provides fault tolerance by generating parity information for the stored data. The system can use the parity information to reconstruct the data on a lost drive even though the parity information does not contain an exact duplicate of all of the stored data. The result is that a RAID 5 array provides more usable disk space than a duplexed or mirrored array but still not as much as a striped array, which contains no redundant data and provides no fault tolerance at all.

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N10-002.03.05.004

Correct Answers: D A. Incorrect: A RAID 5 array does generate parity data, but it does not store all of it on a separate drive. Instead, the parity information is striped across all of the drives along with the data. RAID 3, however, does store all the party data on a single physical drive. B. Incorrect: RAID 5 does not use exact mirroring of the data stored on the array. Instead, it uses parity information, which is a form of ECC the original data generated. In some high-end hardware solutions, RAID 5 arrays can be mirrored to other RAID 5 arrays. C. Incorrect: RAID 5 does not store duplicated data in any form. Storing a duplicate copy of each data stripe on a separate drive would provide fault tolerance and would also improve the array’s overall performance, as compared to mirroring or duplexing entire disks. However, this method would provide no better storage capacity than disk mirroring or duplexing. D. Correct: A RAID 5 array generates parity information for every file it stores and stripes that parity information with the data across all of the drives in the array. This distributes the parity information throughout the array, creating the fault tolerance while improving overall performance and speeding up the data reconstruction process.

N10-002.03.05.005

Correct Answers: B A. Incorrect: A RAID array enables a computer to continue functioning properly after a drive failure but provides no fault tolerance for routers. B. Correct: Creating a redundant backbone and connecting each LAN to it provides two possible routes from each LAN to every other LAN. This way, if a router on one LAN fails, the computers on that LAN can simply use the other router. C. Incorrect: Server clustering enables a server to continue operating despite the failure of one computer in the cluster for any reason, but it provides no fault tolerance for routers. D. Incorrect: ECC is used to generate parity information on a RAID array and to provide error correction in memory chips and other technologies. However, ECC does nothing to aid a network in surviving a router failure.

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3 . 6

Identify the purpose and characteristics of disaster recovery.

Backups are an essential element of network computing. On most computer networks, there is no more valuable resource than the data stored on disk drives and other media, and performing regular backups prevents that data from being irretrievably lost. In most cases, network backup solutions use tape drives to store data because of their large capacity and low media costs. Backing up a network is complicated by the fact that the data that has to be protected is frequently distributed among computers located all over the network. However, the network also aids the backup process by enabling a single drive to back up data located anywhere on the network. The massive increase in the data storage capacity of the typical hard disk drive over the years has made the task of backing up that data increasingly difficult. Tape drive capacities have increased as well (although not at quite the same rate), as have the speeds at which tape drives can store data. However, it is often necessary to back up enormous amounts of data in a relatively short time. The backup window (the time interval during which backups are performed) is frequently limited by the fact that applications must remain running during most of the day, and while they are running, the data files they need are locked open and inaccessible to a typical backup solution. Some high-end solutions have the ability to mark locked files for backup when unlocked. Protecting a greater amount of data in a shorter amount of time is usually accomplished in one of two ways. Either you increase the speed at which data is written to the backup media or you reduce the amount of data that has to be written. You increase the speed of the data transfer by using a faster tape drive or by using multiple tape drives simultaneously. You can reduce the amount of data written to tape by running special jobs that back up only the files that have been used recently. The speed at which data is written to a backup medium is determined not only by the drive, but by the capabilities of the computer hosting the drive and those of the network that delivers the data to the computer hosting the drive. You can purchase the fastest tape drive on the market, but if you connect it to a slow computer with an obsolete interface and a slow network connection, you’ll never realize its full capabilities.

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Readiness Review—Exam N10-002 It is typical to run a backup job on a network every day, but this does not necessarily mean that you have to back up every byte of data on the entire network every day. In most cases, this would require a great many expensive tape drives, and the effort would largely be wasted because much of the data written to tape would be redundant. Computers contain a large number of files that never change, such as the operating system and application program files. If you back these up every day, you end up with identical copies of the same files on your tapes. To save tape and time, backup software products enable you to run jobs that save only the files that have changed recently to tape. A differential backup job, for example, copies only the files that have changed since the last full backup to tape. An incremental backup job copies only the files that have changed since the last full or incremental backup. A typical backup rotation consists of a full backup performed once a week and either a differential or incremental job performed on each of the other days of the week. Incremental and differential backup jobs use the Archive attribute that each file and directory possesses to determine whether it should be backed up. Full backup jobs clear the Archive attributes of all files and directories on a drive. Afterward, whenever an application modifies a file on the drive, the operating system sets the Archive attribute for that file. During an incremental or differential backup, the backup software scans the Archive attribute for each file and backs up only those with the attribute set. Incremental jobs then clear the Archive attributes of all of the files again, while differential jobs leave the attributes alone. The result is that incremental jobs back up only the files changed that day, which takes the minimum amount of time and tape. Differential jobs back up only the files that have changed that week, which requires more time and tape, but which simplifies restoration. To restore a computer backed up using incremental jobs, you must first restore the last full backup tape and then restore each incremental job performed since that full backup. With differentials, you have to restore only the last full backup and the most recent differential. One of the problems with tape-based backup jobs, however, is the time needed to restore the data in the event of a disaster, such as a disk failure. In the event of a complete data loss on a computer, a typical backup solution will require you to reinstall the entire operating system after hardware is repaired or replaced. This is necessary so the backup software can connect to the computer to perform a data restoration. Once the operating system is installed, the restore job can begin, which can easily take several hours depending on how much data is involved and whether the backups used differential or incremental jobs. In some instances, this much down time is unacceptable, and many backup software vendors have addressed this problem by producing specialized disaster recovery products. Disaster recovery software usually takes the form of an add-on product to an existing backup software package that enables you to create a bootable floppy or CD-R disk that provides only enough operating system support to run a stripped-down version of the main backup software program. With this boot disk, you can start up the computer and begin the restore process without reinstalling the operating system first. Since the backup medium contains the full operating system, the restore process brings the computer back to its original state before the disaster.

Objective 3.6

Objective 3.6 Questions N10-002.03.06.001 Which of the following procedures does a disaster recovery product eliminate from a full computer restoration? A. The incremental backup restore B. The full backup restore C. The operating system installation D. The tape drive installation

N10-002.03.06.002 Which of the following backup jobs use the least amount of tape? (Choose two.) A. A full backup B. An incremental backup C. The first differential backup for the week D. The last differential backup for the week

N10-002.03.06.003 Which of the following backup jobs does not clear the Archive attributes of the backed up files? A. A full backup B. A differential backup C. An incremental backup D. A disaster recovery job

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N10-002.03.06.004 Which of the following factors should affect the speed or number of tape drives you select? (Choose two.) A. The amount of data to back up B. The type of data to back up C. The location of the data on the network D. The size of the backup window


Correct Answers: C A. Incorrect: If you use incremental jobs while backing up your data, then you must also perform incrementals during the restoration process regardless of whether you use a disaster recovery product. B. Incorrect: Disaster recovery products make it possible to begin running the restore jobs faster, but they do not affect the actual restoration process. You must still restore your last full backup job to rebuild a failed drive or computer. C. Correct: Disaster recovery products make it possible to boot the computer and run the backup software program without installing the operating system first. D. Incorrect: Disaster recovery products have no effect on the backup solution’s hardware configuration. You still need a tape drive connected to a computer in the usual manner.

N10-002.03.06.002

Correct Answers: B and C A. Incorrect: The first job in any backup solution is a full backup, which is a complete copy of all of the files and directories on the target drive or computer. Because it backs up all possible data, a full backup job uses the most tape of any type of backup. B. Correct: Incremental backup jobs copy to tape only the files that have been changed since the last backup job. If you perform backups daily, then an incremental job contains no more than one day’s worth of data, making it use less tape than most other job types.

Objective 3.6

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C. Correct: The first differential backup job for a week is no different than the first incremental job because each contains only one day’s worth of data. D. Incorrect: Every differential job backs up all the files that have changed since the last full backup. The last differential job for a given week, therefore, consists of all of the files and directories that have been modified since the last full backup job—nearly a week before. This causes it to use much more tape than an incremental job or the first differential job for the week and sometimes nearly as much as a full backup.

N10-002.03.06.003

Correct Answers: B A. Incorrect: A standard full backup job always clears the Archive attributes of all files it backs up in preparation for the incremental or differential jobs that usually occur on subsequent days. B. Correct: Differential jobs do not clear the Archive attributes of the files they back up because the same files backed up in a differential job today will also be backed up in tomorrow’s differential job. In this case, the Archive attributes will not be reset until the next full backup job. C. Incorrect: Incremental backup jobs always clear the Archive bits of the files they back up to use the least amount of time and tape for each job. The drawback of this method is that a full restoration requires you to restore the last full backup and then restore each incremental job performed since that full backup. D. Incorrect: Disaster recovery has no effect on the nature of the backup jobs used to protect the data or the Archive attributes of the data being protected. A disaster recovery product facilitates only the start of the restoration process with a minimum of delay.

N10-002.03.06.004

Correct Answers: A and D A. Correct: Usually, the more data you have to back up, the faster a drive has to be or the more drives you must have to back the data up in a given amount of time. B. Incorrect: The type of data being backed up has no bearing on the speed at which data is written to the job. C. Incorrect: The location of the data on the network has no bearing on the speed of the backup process, except if the network is damaged, preventing data from getting to the backup device. D. Correct: The backup window is the amount of time available to perform a specific backup job. The smaller the backup window is, the faster the drives have to be (or the more you need) to back up a particular target.


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3 . 7

Given a remote connectivity scenario (e.g., IP, IPX, dial-up, PPPoE, authentication, physical connectivity, etc.), configure the connection.

Many networks support access by computers at remote locations using a variety of protocols and physical layer connections. Some networks also use the same type of remote connectivity solution to connect a branch office to the home network when needed. Depending on the bandwidth of the connection used to access the network, the functionality may be far less than that of a locally connected computer, but the user can still access basic services, such as corporate e-mail. At the physical layer of the Open Systems Interconnection (OSI) reference model, the most common type of connection that remote computers use is still a dial-up modem and a Public Switched Telephone Network (PSTN) line. The ubiquity of the PSTN service assures the user a connection from almost any location, and modems are now standard equipment in virtually all computers. Faster connections are also possible using virtually any of the WAN technologies available, such as Integrated Services Digital Network (ISDN). It’s also possible for home users with Internet access using a cable modem or Digital Subscriber Line (DSL) connection to access a company network using a virtual private network (VPN) connection. A VPN connection uses the Internet as a network medium between the remote system and the host network by creating a secured “tunnel” that carries the packets that the two systems exchange. Configuring a network to support remote access can be simple or complex. A single user with a modem-equipped computer on the network can configure it to support remote network access from his home computer using the software provided with most of the operating systems used today. For remote connectivity on a larger scale, network administrators often deploy one or more dedicated servers with specialized remote access hardware, such as a serial hub that makes it possible to connect a large number of modems to a single computer. Alternately, the servers could have a dedicated Internet connection or some other sort of WAN technology. This way, a single server can support a large number of remote users. The most familiar example of this concept to most users is the Internet service provider (ISP), which is simply a company with a high-speed connection to the Internet that resells the bandwidth to subscribers in smaller amounts.

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Readiness Review—Exam N10-002 For the individual remote computers, the physical layer connection usually consists of a standard modem plugged into a bus slot or connected to a serial port, or in the case of higher speed connection, a network interface card connected to a CATV (cable television network) or DSL modem. Most computers support Plug and Play, which makes installing and configuring the modem or network adapter a simple and painless task. At the data-link layer, remote access connections typically use one of two TCP/IP protocols: the Serial Line Internet Protocol (SLIP) or the Point-to-Point Protocol (PPP). SLIP, rarely used anymore, is a simple protocol that performs raw data transfers with no security and virtually no overhead. PPP generates more overhead traffic, but it provides many more features, including multiple network layer protocols and various authentication protocols. There is also a relatively new standard called Point-to-Point Protocol over Ethernet (PPPoE), which enables a remote computer on an Ethernet LAN to establish an individual PPP connection to a server on a host network using a broadband device, such as a cable modem. When you use a cable modem to connect an Ethernet LAN to a remote network (such as the Internet), there is usually only one remote connection involved with a single authentication and network layer protocol configuration. Using PPPoE, a single computer on the remote Ethernet LAN can perform a PPP link establishment procedure to a host server with its own authentication and network layer protocol configuration. This prevents other users on the Ethernet LAN from using the resources to which the PPPoE system has been granted access. At the network and transport layers, remote network connections typically use the TCP/ IP suite, but PPP makes it possible to use NetWare’s IPX protocols either instead of or in addition to TCP/IP. Using these protocols, a computer connected to a remote network can access virtually any Microsoft Windows, NetWare, or UNIX resource. In addition to the physical connection and the data-link, network, and transport layer protocol support, a remote network connection also requires specialized software to use the protocols’ services. All operating systems include the software you need to establish a client connection to a server on a remote network. For example, to configure a dial-up connection to a remote server in Windows 2000, you run the Network Connection Wizard and specify which modem you want to use. You can then use the Dial-up Connection Properties dialog box to specify and configure the protocols you want to use at the data-link, network, and transport layers. Most operating systems include software to configure the computer to operate as a server that can receive incoming connections from remote clients. However, the operating systems’ server capabilities can vary. Windows 2000, for example, can function as a multiprotocol router, enabling a remote user to access both TCP/IP and IPX resources on the network to which the server is connected. Windows 98 cannot route TCP/IP traffic this way. Also, Windows 2000 Server can support up to 256 remote network clients simultaneously, while Windows 2000 Professional can support only one.

Objective 3.7

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Objective 3.7 Questions N10-002.03.07.001 Which of the following physical layer technologies is most commonly used for remote network connections? A. ISDN B. PSTN C. VPN D. PPPoE

N10-002.03.07.002 Which of the following elements must be identical in both the client and server computers to establish a remote network connection? (Choose three.) A. The physical layer connection B. The data-link layer protocol C. The authentication method D. The operating system

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N10-002.03.07.003 A network administrator is assigned the task of configuring the client and server computers for a remote network connection so the client can access a server running NetWare 4.2 on the host network. The client computer is a laptop running Windows 98 and equipped with a standard modem. The server is a Windows 2000 Server computer with an array of 12 modems that is connected to a NetWare network using standard 10 Mbps Ethernet. The administrator configures the client computer to dial in to one of the server’s modems using PPP at the data-link layer and TCP/IP at the network and transport layers. The server is configured to accept incoming calls over its modems using either SLIP or PPP, and its LAN connection is set up to use both TCP/IP and IPX. After completing the configuration process on both computers, the administrator tests the connection by dialing into the server using the client computer. The client successfully connects to the server and can access its resources, but cannot access the NetWare server on the network. Which of the following is a reason for this failure? A. Windows 2000 cannot route IPX traffic. B. The server must be running NetWare for the client to access NetWare resources. C. The client must use SLIP to access NetWare resources. D. The client computer is not configured to use the IPX protocols.


Correct Answers: B A. Incorrect: ISDN provides relatively high-speed connections compared to standard PSTN connections, but it requires special equipment and installation by a telephone carrier. Many of the computers used for remote networking are laptops and other portables, for which ISDN would be impractical. B. Correct: PSTN is the technical name for the standard voice telephone lines available almost anywhere. The majority of remote network connections, and particularly Internet connections, use dialup modems and PSTN lines at the physical layer. C. Incorrect: VPN is a relatively new technology that enables a remote user to access a private network using the Internet as a secured medium. The idea is for the remote computer to use a standard dial-up modem to connect to a local Internet service provider instead of making a long distance call to a server on the host network. While VPNs hold great promise, they are still relatively rare and nowhere near as popular as PSTN connections.

Objective 3.7

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D. Incorrect: PPPoE is a new standard that enables a remote computer to establish a connection to a host server independent of the other computers on its Ethernet network. Like ISDN, this is not a mobile technology because the remote computer must be connected to an Ethernet LAN that is in turn connected to the host network using a broadband device. PPPoE connections have not yet become common.

N10-002.03.07.002

Correct Answers: A, B, and C A. Correct: Although the computers don’t have to use hardware made by the same manufacturer, both must use the same basic type of physical layer connection, such as a modem and PSTN line or an ISDN connection. B. Correct: Both of the computers must use the same data-link layer protocol, such as SLIP or PPP, to establish a remote network connection. This is no different than the computers on a LAN, which must also run the same protocol at the data-link layer, such as Ethernet. C. Correct: Most remote network connections use some form of authentication mechanism, even if it is nothing more than the exchange of a user name and clear text password. To establish the remote network connection, both computers must be configured to use the same type of authentication, even if it is no authentication at all. D. Incorrect: As long as all of the other elements are in place, such as the physical layer connection and the protocols, there is no need for both of the computers involved in a remote network connection to be running the same operating system.

N10-002.03.07.003

Correct Answers: D A. Incorrect: Windows 2000 is perfectly capable of routing both TCP/IP and IPX traffic at the same time and can provide remote users with access to NetWare resources on the host network. B. Incorrect: As long as the server has the proper physical connection hardware and supports the correct protocols, it can provide remote users with access to NetWare resources on the host network regardless of the operating system it is running. C. Incorrect: A remote network client can access NetWare resources on the host network using either SLIP or PPP as long as the server is properly configured to use the same data-link layer protocol as the client’s. D. Correct: To access a NetWare 4.2 server, either on a local or a remote network, a client must be configured to use the IPX protocols. In this case, the server on the host network is properly configured to use both TCP/IP and IPX, but the client is configured to use TCP/IP only. The only change that the administrator needs to make is to add the IPX protocols to the Windows 98 client computer.


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3 . 8

Identify the purpose, benefits, and characteristics of using a firewall.

A firewall is a hardware or software product that is located on the boundary between two networks and protects one from unauthorized access by users on the other. The most common place to find a firewall is at the juncture between a private network and the Internet, although it’s also possible to use a firewall to secure one part of an internetwork from the rest of it. When you use a router to connect your network to the Internet through an ISP, you make it possible for traffic to flow in both directions. Not only can your users request Internet services and receive responses, but unauthorized users on the Internet can also access the computers on your network and do incredible damage. The Internet is rife with unscrupulous individuals who derive pleasure from damaging other people’s property, and these individuals can be very clever. A firewall is your defense against this type of intrusion; it prevents unauthorized traffic from passing through to your network while enabling the traffic your users generate and the responses from Internet servers to get through. A firewall can be integrated into the router that joins two networks or it can be a standalone computer located between the router and the rest of the network. Firewalls use a variety of techniques to protect a network by letting through only the traffic the systems on the protected network need and denying access to everything else. The most basic protection technique is called packet filtering. The firewall examines the packets arriving from outside the protected network and evaluates them based on the information found in their various protocol headers. Most routers include some form of packet filtering capability. Even Windows NT and 2000 have the capability to create basic packet filters. The firewall can use packet filters based on many different packet characteristics, including hardware addresses, IP addresses, protocol identifiers, and port numbers. For example, an administrator might want to enable the network users to access Internet e-mail, but to deny them Web access. By creating filters that enable TCP and User Datagram Protocol (UDP) packets with the port numbers 110 and 25 (the well-known port numbers for POP3 and SMTP) to pass through the firewall, the users can access their Internet e-mail. A filter that prevents packets using port 80, the well-known port

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Readiness Review—Exam N10-002 number for the HTTP used by Web clients and servers, from passing through the firewall denies the users access to Internet Web servers. The creation of packet filters based on port numbers is called service dependent filtering. An effective system of packet filters combines the characteristics used by the various protocols in the networking stack. For example, an administrator may want to enable the network users to access FTP servers on the Internet, but simply opening up ports 20 and 21 (the well-known ports for FTP) would make it possible for Internet intruders to access the computers on the private network using FTP. Therefore, it’s possible to create a combination of packet filters that provide access through ports 20 and 21, but only to the IP addresses of computers that have initiated an FTP connection. Packet filtering can become complex because it is a battle of wits between the network administrator or firewall designer and a continuously innovative class of Internet intruder. Packet filtering assumes that the computers on the private network are using registered IP addresses that make them vulnerable to outside attacks. A registered IP address is intended to be visible from the Internet. However, many of the networks connected to the Internet today do not use registered IP addresses but use addresses in special ranges designated for use on private networks. These unregistered addresses are not visible from the Internet, and the task of a firewall in this case is to make it possible for the computers on the private network to communicate with Internet servers despite not having registered addresses. Network address translation (NAT) is one of the most common techniques used to provide Internet access to computers with unregistered IP addresses. In a NAT implementation, all of the client computers on the network have unregistered IP addresses, which makes them visible to other computers on the private internetwork but not to computers on the Internet. For the clients to access Internet services, a router on the internetwork functions as a NAT server. The NAT server is the only computer on the network with a registered IP address, enabling it to interact directly with Internet computers. The unregistered clients on the network use the NAT server as their default gateway to the Internet. When a client requests access to an Internet service, the request packet goes through the NAT server. The NAT server modifies the packet’s IP header by substituting its own registered IP address for the client’s unregistered address. The server then forwards the packet to the appropriate server on the Internet, which processes it in the normal manner. Because the Internet server knows only that it received a request from the NAT server, it returns its replies to the NAT server’s address. The NAT server then modifies the response packets, now substituting the original client’s unregistered address for its own registered one and forwarding the responses to the client. By modifying the packet headers, the NAT server makes it appear to the client as though it is accessing the Internet server directly and makes it appear to the Internet server as though the request originated from a client with a registered IP address. Because NAT functions at the network layer of the OSI reference model, it works with any TCP/IP application and requires no modifications to the application software or to the system configuration (other than the use of the correct default gateway address).

Objective 3.8

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Objective 3.8 Questions N10-002.03.08.001 NAT operates at which layer of the OSI reference model? A. Data-link B. Network C. Transport D. Application

N10-002.03.08.002 Service dependent filtering uses which of the following elements to grant or deny packets access to a private network? A. IP addresses B. Hardware addresses C. Protocol identifiers D. Port numbers

N10-002.03.08.003 A network administrator is installing a computer to function as a firewall protecting a corporate internetwork from Internet intrusion. Where should he install the firewall system? A. Anywhere on the private internetwork, as long as the Internet is accessible B. Between the Internet access router and the ISP’s network C. At the ISP’s network site D. Between the Internet access router and the rest of the private internetwork

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Correct Answers: B A. Incorrect: NAT works by modifying IP addresses, which are a network layer element. The datalink layer is concerned with only communications on the local network and is not involved with NAT processing. B. Correct: NAT modifies the IP headers of packets traveling to and from the Internet, and IP is a network layer protocol. C. Incorrect: NAT modifies only the IP packet headers, and IP is a network layer protocol. For this reason, NAT works with any transport layer protocol. D. Incorrect: NAT works with any TCP/IP application because it operates below the application layer of the OSI model (at the network layer). An application layer firewall product, such as a proxy server, requires each application to be individually configured to use the server. NAT requires no reconfiguration of the applications that use it.

N10-002.03.08.002

Correct Answers: D A. Incorrect: IP addresses are not service-specific because they operate at the network layer of the OSI model. A packet filter that is based on IP addresses affects all traffic to or from a particular computer, not just that associated with a specific service. B. Incorrect: Hardware addresses are, in most cases, coded into network interface adapters. A packet filter that works with hardware addresses is a method for granting or restricting all access to or from a specific computer while making it impossible for an unauthorized user to “spoof” the firewall by changing IP addresses. C. Incorrect: Protocol identifiers are used by data-link layer protocols to specify which network layer protocol generated the data carried in a packet. A network layer protocol can carry information generated by any application, so it is not service-specific. D. Correct: Port numbers are the codes used by transport layer protocols such as TCP and UDP to identify the application or service that generated the data carried in a packet. Service dependent filtering uses port numbers to limit traffic based on specific applications.

Objective 3.8

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N10-002.03.08.003

Correct Answers: D A. Incorrect: The firewall acts as a barrier between the private network and the Internet. If the firewall was located in the midst of the private internetwork, it would be possible for Internet computers to bypass the firewall and communicate directly with the private systems. B. Incorrect: The router is the delimiter between the ISP’s network and the private internetwork. Placing the firewall on the far side of the router would put it on the ISP’s network, causing it to filter all of the ISP’s traffic and not just that destined for the private network. C. Incorrect: Installing the firewall at the ISP’s site would have the same effect as installing it on the far side of the router at the private network site. The firewall would receive and process all of the packets on the ISP’s network instead of just those intended for the private network. D. Correct: The firewall is a conduit between the private network and the ISP’s network (which provides access to the Internet), through which all traffic must pass. This ensures that the firewall has the opportunity to examine every packet that passes between the private network and the Internet and filter out those that are not authorized.


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3 . 9

Identify the purpose, benefits, and characteristics of using a proxy.

A proxy server is a type of firewall technology that enables client computers on a private internetwork to access Internet services without leaving the network open to potential intruders. A proxy server functions like a NAT server in that it acts as an intermediary between clients on the private network and Internet servers, making external requests on the clients’ behalf. As with NAT, the clients on the private network use unregistered IP addresses and the proxy server uses a registered address. The clients do not have access to a router that provides Internet access; all Internet communications go through the proxy server. A client generates a request for Internet services and sends it to the proxy server, which then issues its own duplicate request to the proper Internet server. The Internet server responds to the proxy server and the proxy server forwards the response to the client that originally generated the request. The main difference between a proxy server and a NAT server is that the proxy server functions at the application layer of the OSI reference model and NAT servers operate at the network layer. Because proxy servers operate at the application layer, they work only with specific application layer protocols. It’s typical for a proxy server to support basic Internet protocols, such as the HTTP used on the Web, the FTP, and the SMTP used for Internet e-mail. Some proxy servers also include support for video conferencing and other streaming media. Because proxy servers work at the application layer, they cannot use the default gateway setting as a native mechanism for getting client traffic to the proxy server. NAT servers are integrated into routers, and because both function at the network layer, the default gateway setting is a natural means of routing all client traffic to the NAT server. This is a natural solution because NAT is not application-specific. By contrast, proxy server clients must send only the traffic generated by specific applications, such as Web browsers and e-mail clients, to the proxy server. As a result, each supported application on a client computer has to be configured to send its traffic to the proxy server instead of to the default gateway (which does not provide access to the Internet). The client computers must use applications that have built-in support for using a proxy server or install the proxy client software that is usually bundled with the proxy server

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Readiness Review—Exam N10-002 software. This is also unlike NAT, which can use any application with no modification. As originally conceived, it was necessary for a user or administrator to manually configure each application on every proxy client with the proxy server’s address. This was a major impediment to deploying proxy servers on large networks. Today, however, there are a variety of technologies available that enable clients to automatically detect a proxy server and send the appropriate traffic to it. It is still necessary to modify the client computers by installing a special client software package or by configuring an application to automatically detect the proxy server. But the process is generally much easier than it used to be, making proxy servers a practical solution for large networks. Another byproduct of the fundamental difference between a proxy server and a NAT server is that proxy servers are capable of working with the application layer data they receive. A NAT server is basically an enhanced router, and the convenience derived because it works with all network layer traffic also means that it has no control over the information carried inside the network layer datagrams. A proxy server is not simply a middleman between the client computer and the Internet server. The proxy server actually generates its own Internet service requests from the packets it receives from clients, receives the Internet servers’ responses, and then repackages the data for delivery to the client. In the process, the proxy server reads the application layer data in the packets and can provide a variety of additional services, such as caching and scanning. Many proxy servers are able to cache the Web pages they receive from the Internet internally. If another client issues a request for the same Web page as a previous client, the proxy server can satisfy the request using cached data instead of generating a duplicate Internet request. This increases the speed at which the client receives the data and conserves bandwidth on the Internet connection. Some proxy server products have more advanced caching features, such as the capability to automatically refresh the most requested pages in the cache. It is also possible to configure multiple proxy servers in an array as way to load-balance requests in large corporate offices. On receiving data from the Internet, it’s also possible for most proxy servers to scan it for viruses or other potentially dangerous software, as well as for undesirable content, before passing it on to the client. Proxy servers can also log the network users’ Internet activities, enabling the administration to monitor their usage patterns and screen the Internet sites they are accessing. Proxy servers also have the ability to control hours of access for all users or certain groups of users. These features enable network administrators to exercise a much greater degree of control over the users’ Internet activities than they could with a NAT server.

Objective 3.9

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Objective 3.9 Questions N10-002.03.09.001 The president of a company running a 500-node private internetwork has ordered the director of network administration to connect the network to the Internet. The primary objective of the project is to provide all of the users on the network with access to Internet Web and e-mail services while keeping the client computers safe from unauthorized users on the Internet. The secondary objectives of the project are to avoid having to modify each one of the client computers individually and to provide a means of monitoring and regulating the users’ access to the Internet. The network administrator submits a proposal calling for the use of unregistered IP addresses on the client computers and a series of proxy servers with registered IP addresses, which are connected to the Internet using multiple T-1 lines. Which of the following statements about the proposed Internet access solution is true? A. The proposal fails to satisfy both the primary and secondary objectives. B. The proposal satisfies the primary objective but neither of the secondary objectives. C. The proposal satisfies the primary objective and one of the secondary objectives. D. The proposal satisfies the primary objective and both of the secondary objectives.

N10-002.03.09.002 Proxy servers operate at which layer of the OSI reference model? A. Data-link B. Network C. Transport D. Application

N10-002.03.09.003 Which of the following statements accounts for the security against outside intrusion provided by proxybased Internet access? A. The proxy server uses a registered IP address and the client computers use unregistered addresses. B. The proxy server uses an unregistered IP address and the client computers use registered addresses. C. Both the proxy server and the client computers use registered IP addresses. D. Both the proxy server and the client computers use unregistered IP addresses.

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N10-002.03.09.004 Which of the following statements about proxy servers and NAT servers are true? (Choose two.) A. NAT servers and proxy servers can both provide Internet access to clients running any application. B. NAT servers and proxy servers both use registered IP addresses. C. NAT servers and proxy servers both access Internet servers and relay the responses to network clients. D. Both NAT servers and proxy servers cache Web data for later use.


Correct Answers: C A. Incorrect: The proxy server installation as proposed will provide the network users with access to the Internet, and the use of unregistered IP addresses on the client computers protects them from Internet intrusion, thus satisfying the primary objective. B. Incorrect: The proposal satisfies the primary objective by providing Internet access to the network’s users and by protecting the client computers from unauthorized access via the Internet. Proxy servers also enable network administrators to monitor users’ Internet access patterns, thus satisfying at least one of the secondary objectives. C. Correct: Proxy servers provide network users with access to Internet services, and the unregistered IP addresses on the client computers protect them from unauthorized access by users on the Internet, which satisfies the first objective. The proxy servers also make it possible for network administrators to regulate users’ access to the Internet, which satisfies one of the two secondary objectives. D. Incorrect: The proposal provides Internet access and protection from outside intrusion in the form of proxy servers, as well as a means for monitoring and regulating the network users’ Internet activities, which satisfies the primary object and one of the secondary objectives. However, proxy servers require that each of the client computers be reconfigured or have additional software installed, so the proposal does not satisfy one of the secondary objectives.

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Correct Answers: D A. Incorrect: A proxy server cannot be a data-link layer device because it can provide Internet access to an entire internetwork, and the data-link layer is concerned solely with LAN communications. B. Incorrect: Proxy servers are designed to function with specific applications. Therefore, proxy servers cannot be network layer devices because the network layer handles all internetwork packets indiscriminately and is unaware of what application generated the data carried inside the packets. C. Incorrect: Transport layer processes provide services to network layer protocols, such as guaranteed delivery and flow control, and they do identify the application layer protocol that generated the data inside each packet. However, the transport layer is not involved in processing application data, so proxy servers cannot be said to function at the transport layer. D. Correct: A proxy server is an application layer service because it receives Internet service requests from client computers, reads the application layer protocol data in each request, and then generates its own request for the same service and transmits it to the Internet server the client specifies. Only an application layer service can read and process the application layer data in network packets.

N10-002.03.09.003

Correct Answers: A A. Correct: Because the client computers use unregistered IP addresses, they are invisible to the Internet, so users outside the private network cannot see or access them. The proxy server has a registered IP address so it can participate in service transactions with Internet servers. B. Incorrect: If the proxy server used an unregistered IP address, it would not be able to access the Internet directly. If the clients used registered IP addresses, they would be visible to the Internet and vulnerable to intrusion. C. Incorrect: The proxy server must have a registered IP address in order to communicate directly with the Internet. However, using registered addresses on the client computers would eliminate the need for a proxy server because the clients could access the Internet directly, and it would leave them vulnerable to intrusion. D. Incorrect: If both the proxy server and the client computers use unregistered IP addresses, neither would be able to communicate with the Internet.

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Correct Answers: B and C A. Incorrect: Because NAT servers function at the network layer, clients can use any application to access the Internet through the server. Proxy servers, however, operate at the application layer, and can provide Internet access only to certain types of client applications. B. Correct: In order to provide clients with Internet access, a NAT or proxy server must have direct access to the Internet, which requires using a registered IP address. C. Correct: Although they operate at different layers of the OSI model, both NAT and proxy servers function as the middleman in transactions between the client computers on a private network and Internet servers. The NAT or proxy transmits the client’s service request to the Internet server as if it was its own and, after receiving the reply, relays the response back to the client. D. Incorrect: Only proxy servers are capable of caching Web data for later use because only they are application layer processes that read the application layer protocol data in the message packets they receive. NAT servers are network layer processes that forward packets with no knowledge of the application layer information in their contents.

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3 . 1 0

Given a scenario, predict the impact of a particular security implementation on network functionality (e.g., blocking port numbers, encryption, etc.).

Network security is always a tradeoff between functionality and protection. The ultimate in a secure network would be one in which nobody has any access to any resources, but this would hardly be useful. When implementing network security features, the idea is to provide adequate protection without reducing user convenience and system performance to the point at which productivity declines. A secure network is usually one that combines a variety of security features provided by the network’s hardware and software components. Each of the security mechanisms you elect to use on your network has an impact on the network’s functionality. With some mechanisms, the impact is so slight as to be imperceptible, while others can profoundly affect the network’s performance and usability. It is up to the network administrator to determine which security measures are necessary for the users, the data, and the organization, and to select and implement them in such a way as to minimize the impact on network functionality. Firewall technologies can affect network functionality in several ways. The firewall’s processing of the data packets can introduce delays, and the firewall’s protective functions can limit the tasks that users are able to perform. For example, packet filtering can slow the rate at which a router processes data packets. The amount of performance degradation depends on the number and complexity of the filters in place. If a network administrator creates a long list of packet filters designed to provide users with as much access to the Internet as possible while maintaining adequate security, the router takes longer to process each packet. The delay incurred by packet filtering adds to the router’s latency, that is, the delay incurred as the router processes each packet. The more traffic the router has to process, the greater the latency.

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Readiness Review—Exam N10-002 Packet filtering can also affect users’ Internet activities. A network administrator can use packet filtering to prevent network users from accessing specific Internet services or even specific Internet servers. For example, you may want to provide your users with Internet e-mail functionality but prevent them from surfing the Web during business hours. You can implement a service-dependent packet filter that blocks all traffic using port 80, which is the well-known port assigned to the HTTP used for Web communications. At the same time, the filters can allow traffic through using well-known ports 25 and 110, which are assigned to the SMTP and the POP3, respectively. In some cases, filters can prevent a user from accessing an Internet service that uses a non-standard port, such as a streaming media application. When this is the case, it is up to the network administrator to decide whether to modify the filters to open up the appropriate port or to deny the user access to that service. NAT and proxy servers can also impact network functionality. NAT does not restrict user access to particular services because it works at the network layer and modifies all packets traveling to and from the Internet. However, the process of modifying the IP header of every packet passing through the NAT server introduces another element of latency. In the case of NAT, the amount of latency is based solely on the network traffic level and is more easily quantifiable than the latency packet filtering causes. Proxy servers are an unusual case in that they can slow clients’ Internet performance at some times and speed it up at others. As with NAT, a proxy server processes every Internet service request a network client generates. Since proxy servers operate at the application layer of the OSI model, the amount of processing involved is larger than that of a NAT server, which increases the latency. However, if a client issues a request for an Internet home page that is stored in the proxy server’s cache, the access speed is increased because the proxy server can satisfy the cache’s request without sending a new request over the Internet. Another security mechanism that can have a profound effect on network functionality is data encryption. Encrypting data is a processor-intensive procedure, and the effort that a computer must put into the encryption process can slow its overall performance. There are a number of network security features that use encryption in different ways. Authentication protocols, such as Kerberos, transmit passwords in encrypted form to avoid having them intercepted by unauthorized users on the network. In this case, the amount of data being encrypted is small and the effect on the network is minor. However, you can use security mechanisms, such as IPsec, to encrypt all of the data transmitted over a network, and in this case the impact on network functionality can be profound. Depending on the amount of data involved and the capabilities of the computers, the process of encrypting the data before transmission and decrypting it afterwards can introduce a great deal of additional latency that results in a noticeable degradation of network performance. Security mechanisms such as IPsec should be used only in cases in which they are definitely needed.

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Objective 3.10 Questions N10-002.03.10.001 The impact of data encryption on a network’s functionality is based primarily on which of the following factors? (Choose two.) A. The algorithm used to encrypt the data B. The amount of data being encrypted C. The protocol that generated the data to be encrypted D. The speed of the computers performing the encryption

N10-002.03.10.002 Which of the following security mechanisms can have a positive influence on network functionality? A. Packet filtering B. NAT C. A proxy server D. Data encryption


Correct Answers: B and D A. Incorrect: Although the type of encryption a particular security mechanism uses can have an impact on the network’s functionality, it is not the primary factor in determining the degree of impact. B. Correct: The more data there is to encrypt, the more processor time is needed to perform the encryption. Therefore, a security mechanism that requires more data to be encrypted has a more profound impact on the network’s functionality. C. Incorrect: The process of encrypting data is not greatly affected by the type of data being encrypted, so the protocol that generated the data is inconsequential to the impact the encryption process has on the network’s functionality. D. Correct: Data encryption is a highly processor-intensive task, so a faster computer is able to encrypt data more quickly and reduce the amount of latency that affects network functionality.

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Correct Answers: C A. Incorrect: Packet filtering’s effect on a network’s functionality can vary greatly depending on the number and type of filters involved, but however small the effect is, it is still negative. B. Incorrect: Because a NAT server processes every packet it receives in the same way, its effect on network functionality is consistent and predictable. However, it is always a negative effect because the additional processing the NAT server performs always introduces a delay, however small. C. Correct: When a proxy server relays a client’s service request to the Internet, the generation of the duplicate request by the server and the processing of the reply invariably introduces a certain amount of latency to the network. However, when the proxy server has the information the client requests stored in its cache, it can return a response to the client faster than if it had to send a request to the Internet server, and faster even than if the client was able to send the request to the Internet server itself. D. Incorrect: Data encryption always has a negative effect on network functionality to some degree because the encryption procedure adds latency to the network communications process.

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3 . 1 1

Given a network configuration, select the appropriate NIC and network configuration settings (DHCP, DNS, WINS, protocols, NetBIOS/host name, etc.).

To connect computers to a network, you not only have to install the appropriate hardware, such as network interface adapters, also known as network interface cards (NICs), cables, and hubs, you also have to configure the computer with the appropriate settings for network communication. Depending on the hardware involved and the services available on the network, the computer configuration process may be almost entirely automated or you may have to configure it manually. The parameters that have to be configured are as follows.

NIC settings—Most NICs, computers, and operating systems support the Plug and Play standard, which enables the system to automatically install the appropriate driver for a new hardware component and configure both the hardware and software to operate properly. In the rare event that your hardware does not support Plug and Play, or if the automatic configuration process fails, you may need to manually configure the NIC, the NIC driver, or both. For a NIC to function, it and its driver must both be configured to use the same hardware resources, such as an interrupt request (IRQ) and an I/O port address. To manually configure the NIC, you use a program supplied by the manufacturer. To configure the NIC driver, you use an interface supplied as part of the driver, which is typically integrated into the operating system. In Windows, for example, the NIC driver configuration interface is a standard, tabbed Properties dialog box. Clients—Many operating systems require you to install a client for the particular type of network you’re running, which consists largely of a module that enables applications running on the computer to access network resources. In Windows, the client includes a module called a redirector, which takes application requests for resources usually found on the local system, such as files and printers, and forwards

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Readiness Review—Exam N10-002 them to the appropriate server on the network. Windows includes clients for Microsoft Windows networks and for NetWare networks; you can use the Windows Control Panel to install either or both.

Protocols—For a computer to communicate with a network, they must have protocols in common. In this context, protocols refers to a suite of protocols spanning the OSI reference model from the network to the application layer, such as TCP/IP, IPX, or NetBEUI. Most operating systems install these protocol suites as a single software module. TCP/IP is by far the most popular protocol suite, but as long as all of the computers on your network run the same protocols, they will be able to communicate. NetBIOS/host name—On most networks, each computer is assigned a unique name for identification purposes. On networks running TCP/IP, the name is just a human convenience because the computers on the network use IP addresses to identify each other. On networks running NetBIOS, however, the name assigned to each system is its only identification. These identifying names are referred to by different terms depending on the mechanism used to register them. On Windows networks, they are technically called NetBIOS names, although the Control Panel interface calls them simply computer names. On TCP/IP networks that use DNS for computer identification, the computer is known as a host and its name as a host name. If your network uses the TCP/IP protocols as most do, then you must configure several TCP/IP parameters on each computer, either automatically or manually. The mechanism for automatically configuring TCP/IP clients is called the Dynamic Host Configuration Protocol (DHCP). To use DHCP, you must be running a DHCP server on your network. A DHCP server is a software application included with most server operating systems that maintains a database of TCP/IP settings, assigns (leases) them to client computers as needed, and reclaims them when they are left unused. By default, the Windows operating systems are configured to use DHCP. If you do not have a DHCP server on your network, then you must manually configure the following parameters, using an interface such as the Windows Control Panel:

IP address—The IP address is a 32-bit value that uniquely identifies the network interface in a device on a TCP/IP network. Every computer on a TCP/IP network must have a unique IP address. One of the major strengths of DHCP is its capability to assign a different address to each computer and keep track of the assignments, thus relieving the network administrator of a particularly onerous task.

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Subnet mask—The subnet mask is a 32-bit value that specifies which bits of the IP address identify the network and which identify the host on that network. Default gateway—The default gateway setting contains the IP address of a router on the local network that the computer should use to send traffic to systems on other networks. DNS servers—A Domain Name System (DNS) server is an application that resolves host and domain names into IP addresses. On TCP/IP networks, host names and domain names exist primarily for the users’ benefit and the TCP/IP protocols use IP addresses to identify other systems in their communications. For users to be able to specify the host names of computers in their applications (such as Web browsers), they must have access to a DNS server, the address of which you specify as part of the TCP/IP configuration. The DNS server receives requests from clients containing host and domain names and responds with the IP addresses associated with those names. WINS servers—The Windows Internet Name Service (WINS) is a server application that performs a similar function to DNS, except that it works with the NetBIOS names Windows networks use instead of host and domain names. Prior to Windows 2000, Microsoft Windows network relied heavily on NetBIOS names to identify resources on the network, and WINS is the best method for resolving NetBIOS names into IP addresses. Windows 2000 introduced Active Directory, however, which uses DNS names instead of or in addition to NetBIOS names. Configuring a client computer to use WINS is no different than the DNS configuration. You specify the address of one or more WINS servers on the network in the Windows Control Panel.

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Objective 3.11 Questions N10-002.03.11.001 Which of the following parameters is not part of the TCP/IP client configuration? A. The default gateway B. The NetBIOS name C. The subnet mask D. The WINS server address

N10-002.03.11.002 Under which of the following circumstances must you manually configure a NIC? A. The network uses the NetBEUI protocols. B. There is no DHCP server on the network. C. The NIC does not support Plug and Play. D. You are connecting the computer to the network for the first time.

N10-002.03.11.003 After installing a Plug and Play NIC into a new Windows NT computer and connecting it to a TCP/IP network with a DHCP server running on it, which of the following parameters must the network administrator configure manually? A. The subnet mask B. The IRQ C. The WINS server address D. The NetBIOS name

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Correct Answers: B A. Incorrect: The default gateway is part of the TCP/IP configuration. To send IP traffic to systems on other networks, a computer must have access to a router, and the default gateway setting specifies the address of a router on the local network. B. Correct: Although NetBIOS names can be resolved into IP addresses on TCP/IP networks, the NetBIOS name space is wholly independent of the TCP/IP protocols. C. Incorrect: The subnet mask is an essential component of the TCP/IP configuration. Without it, the computer has no way of knowing which bits of the IP address identify the network and which identify the host on that network. D. Incorrect: A WINS server’s function is to resolve NetBIOS names into IP addresses so a TCP/IP network can use NetBIOS names to identify specific devices on the network.

N10-002.03.11.002

Correct Answers: C A. Incorrect: The selection of the protocols used at the network layer and above has no bearing on the NIC’s configuration or its driver’s. B. Incorrect: DHCP is a service that automatically configures TCP/IP clients on a network and is not involved in the physical and data-link layer processes a NIC performs. C. Correct: Plug and Play is the standard that enables a computer to automatically install and configure a NIC driver. Without Plug and Play, you must manually configure both the NIC and its driver to use the same hardware settings—settings that are acceptable to the computer as well. D. Incorrect: Plug and Play can automatically configure a hardware device the first time you install it into a computer. You don’t ever have to manually configure a NIC when all of the components involved support Plug and Play and that mechanism is functioning properly.

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Correct Answers: D A. Incorrect: The DHCP server can supply a subnet mask to the computer automatically, along with an IP address. B. Incorrect: Part of the procedure by which Plug and Play installs and configures a new hardware device like a NIC is choosing a suitable IRQ that enables the device to communicate with the computer. C. Incorrect: A DHCP server can supply a WINS server address to a client computer along with the other TCP/IP configuration parameters. D. Correct: DHCP cannot automatically supply unique NetBIOS names to client computers, nor is Plug and Play involved in the process of NetBIOS name assignment. You must manually specify a unique NetBIOS name for every computer on the network.

O B J E C T I V E

D O M A I N

4

Network Support

Building a network starts with components such as computers, network interface adapters, cables, and hubs, but there are many other hardware and software elements involved in network communications. To construct an efficient, useful, and secure network, you must also consider the characteristics of the client and server operating systems you plan to use, paying particular attention to their interoperability and security. There are also other technologies that you may want to integrate into your network— technologies that can provide additional security, data storage, and network administration services.

Tested Skills and Suggested Practices The skills that you need to successfully master the Network Support objective domain on the Network+ Certification exam include:

Given a troubleshooting scenario, selecting the appropriate TCP/IP utility from among the following: Tracert, Ping, Arp, Netstat, Nbtstat, Ipconfig/ Ifconfig, Winipcfg, and Nslookup. Practice 1: On a network workstation, run each of the specified utilities (except for Winipcfg, which is a graphical utility) with no parameters or with the /? parameter to display the help screens for each one. Examine the parameters for each of the programs and the functions it provides. Practice 2: Run the TRACERT.EXE utility on an Internet-connected Windows computer, using the name of an overseas Web server as the target. Examine the elapsed times for each hop in the path to the target and note where the path crosses the ocean.

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Given a troubleshooting scenario involving a small office/home office network failure (for example, xDSL, cable, home satellite, wireless, PSTN), identifying the cause of the failure. Practice 1: Study the Websites of DSL, cable, and satellite Internet service providers to determine how they provide Internet connectivity. Practice 2: Compare the relative speeds, costs, reliability, and access limitations of the various small network technologies listed here. Given a troubleshooting scenario involving a remote connectivity problem (for example, authentication failure, protocol configuration, physical connectivity) identifying the cause of the problem. Practice 1: Configure a Windows test computer to connect to a remote network using a dial-up modem and telephone line. Examine the various configuration parameters provided and use the Windows online help to determine their functions in relation to the connection process. Practice 2: Induce connectivity problems on your test computer by disconnecting the telephone line, removing a vital protocol, and deliberately supplying an incorrect authentication password. Observe how the resulting errors are manifested. Given specific parameters, configuring a client to connect to the following servers: UNIX/Linux, NetWare, Windows, Macintosh. Practice 1: Study the network configuration interface on computers running the various Windows operating systems and compare the locations of the various parameters. Practice 2: List the configuration parameters required to connect a client workstation to each of the server operating systems listed. Given a wiring task, selecting the appropriate tool (for example, wire crimper, media tester/certifier, punch down tool, tone generator, optical tester). Practice 1: Obtain some of the basic cabling components, such as bulk cables, connectors, and a crimper, and practice assembling network cables. Practice 2: Obtain a cable tester of one of the specified types and use it to examine your lab network for cabling faults. Given a network scenario, interpreting visual indicators (for example, link lights, collision lights) to determine the nature of the problem. Practice 1: Examine the equipment used to construct your lab network, and make a list of all of its lights and other visual indicators.

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Practice 2: Using the documentation for your lab network hardware, such as your hubs and network interface adapters, or the manufacturers’ Web sites, determine the functions of the lights and other visual indicators in your list. Given output from a diagnostic utility (for example, tracert, ping, ipconfig), identifying the utility and interpreting the output. Practice 1: Run each of the utilities listed with all of their various command line parameters and observe how the parameters modify the output. Practice 2: Print the output generated by each of the diagnostic utilities listed, shuffle the printouts, and learn to identify each of the utilities by its output display. Given a scenario, predicting the impact of modifying, adding, or removing network services (for example, DHCP, DNS, WINS) on network resources and users. Practice 1: Using the Windows 2000 Performance console, observe the effect that installation of each of the network services listed has on a Windows 2000 server in terms of memory use and network traffic. Practice 2: Compare the performance of a Windows network workstation using WINS to resolve NetBIOS names with that of one using broadcast name resolution. Given a network problem scenario, selecting an appropriate course of action based on a general troubleshooting strategy. Practice 1: Determine the most common problems that occur on your organization’s network and try to isolate the cause using this procedure. Practice 2: Using specific troubleshooting scenarios, determine how eliminating each of the steps in the procedure would negatively affect the overall problem solving effort. Given a troubleshooting scenario involving a network with a particular physical topology (that is, bus, star/hierarchical, mesh, ring, and wireless) and including a network diagram, identifying the network area affected and the cause of the problem. Practice 1: Study the various cabling topologies used for local area networks and the vulnerability of each one to cable breaks and other faults. Practice 2: Create a diagram of your network and modify it to show various types of faults that can affect its functionality.

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Given a network troubleshooting scenario involving a client connectivity problem (for example, incorrect protocol/client software/authentication configuration, or insufficient rights/permission), identifying the cause of the problem. Practice 1: Configure a lab workstation with an incorrect protocol or other client software module and then attempt to connect to a server. Observe the workstation under these conditions and the error messages generated. Practice 2: Using a properly configured client workstation, attempt to log on to a network server using an incorrect authentication password or try to access resources to which your account does not have sufficient rights or permissions, and observe the error messages the client generates. Given a network troubleshooting scenario involving a wiring/infrastructure problem, identifying the cause of the problem (for example, bad media, interference, network hardware). Practice 1: On a lab network that you have permission to modify, induce media problems such as broken or miswired cables or loose connectors, and see how they affect the network’s performance. Practice 2: Study the cabling guidelines for the Ethernet networks and learn how improperly installed and configured cables affect network performance.


Objective 4.1 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 2 in Chapter 10, “TCP/IP Applications.” Microsoft Corporation. Windows 2000 Server Resource Kit. Volume: TCP/IP Core Networking Guide. Redmond, Washington: Microsoft Press, 2000. Review Chapter 3, “TCP/IP Troubleshooting.”

Objective 4.2 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lessons 1 and 3 in Chapter 12, “Remote Network Access.” Microsoft Corporation. Microsoft Encyclopedia of Networking. Redmond, Washington: Microsoft Press, 2000. See entries for cable modem, Digital Subscriber Line (DSL), remote access, and wireless networking.

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Objective 4.3 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lessons 1 and 2 in Chapter 11, “TCP/IP Configuration,” and Lessons 1, 2, and 3 in Chapter 12, “Remote Network Access.” Microsoft Corporation. Windows 2000 Server Resource Kit. Volume: Deployment Planning Guide. Redmond, Washington: Microsoft Press, 2000. Review Chapter 22, “Defining a Client Connectivity Strategy.”

Objective 4.4 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lessons 1 and 2 in Chapter 4, “Networking Software.” Microsoft Corporation. Windows 2000 Server Resource Kit. Volume: Deployment Planning Guide. Redmond, Washington: Microsoft Press, 2000. Review Chapter 22, “Defining a Client Connectivity Strategy.”

Objective 4.5 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 2 in Chapter 15, “Installing a Network,” and Lesson 3 in Chapter 18, “Network Troubleshooting Tools.” Microsoft Corporation. Microsoft Encyclopedia of Networking. Redmond, Washington: Microsoft Press, 2000. See entries for cable tester, crimper, and fiber optic cabling.

Objective 4.6 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 2 in Chapter 18, “Network Troubleshooting Tools.” Spurgeon, Charles. “Quick Reference Guide to Auto-Negotiation.” This document is available at Charles Spurgeon’sWeb site at http://wwwhost.ots.utexas.edu/ethernet/ 100quickref/ch13qr_1.html.

Objective 4.7 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 2 in Chapter 10, “TCP/IP Applications.” Microsoft Corporation. Windows 2000 Server Resource Kit. Volume: TCP/IP Core Networking Guide. Redmond, Washington: Microsoft Press, 2000. Review Chapter 3, “TCP/IP Troubleshooting.”

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Objective 4.8 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 1 in Chapter 10, “TCP/IP Applications.” Microsoft Corporation. Windows 2000 Server Resource Kit. Volume: TCP/IP Core Networking Guide. Redmond, Washington: Microsoft Press, 2000. Chapter 4, “Dynamic Host Configuration Protocol,” Chapter 5, “Introduction to DNS,” Chapter 6, “Windows 2000 DNS,” and Chapter 7, “Windows Internet Name Service.”

Objective 4.9 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 2 in Chapter 17, “Network Troubleshooting Procedures.” Microsoft Corporation. Windows 2000 Server Resource Kit. Volume: Operations Guide. Redmond, Washington: Microsoft Press, 2000. Review Chapter 14, “Troubleshooting Strategies.”

Objective 4.10 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 1 in Chapter 2, “Network Hardware.” Microsoft Corporation. Microsoft Encyclopedia of Networking. Redmond, Washington: Microsoft Press, 2000. See entries for bus topology, mesh topology, ring topology, star bus topology, star topology, and topology.

Objective 4.11 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 2 in Chapter 4, “Networking Software.” Microsoft Corporation. Windows 2000 Server Resource Kit. Volume: Deployment Planning Guide. Redmond, Washington: Microsoft Press, 2000. Review Chapter 22, “Defining a Client Connectivity Strategy.”

Objective 4.12 Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lessons 1 and 2 in Chapter 15, “Installing a Network.” Microsoft Corporation. Windows 2000 Server Resource Kit. Volume: Operations Guide. Redmond, Washington: Microsoft Press, 2000. Review Chapter 14, “Troubleshooting Strategies.”

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4 . 1

Given a troubleshooting scenario, select the appropriate TCP/IP utility from among the following: Tracert, Ping, Arp, Netstat, Nbtstat, Ipconfig/Ifconfig, Winipcfg, Nslookup.

Virtually all of the operating systems used on networks include a TCP/IP (Transmission Control Protocol/Internet Protocol) client, and in addition to the components that provide the actual TCP/IP connectivity, the client typically includes a variety of utilities that enable you to test and display information about TCP/IP functions. Most of these utilities are character-based programs, with command line parameters that are similar or identical to the implementations provided with various operating systems. Some of these utilities, such as Ping, should be a regular part of your network troubleshooting toolkit, while others are more seldomly used. The most commonly used TCP/IP utilities are as follows:

Tracert—TRACERT.EXE is the Windows equivalent of a UNIX utility called traceroute, which displays the path that TCP/IP packets take through an internetwork to their destination. When the packets generated by a particular computer fail to reach their destination, you can use Tracert to determine exactly how far they are getting before encountering a condition that stops their progress. This enables you to isolate the location of the problem. To use Tracert, you execute the program from a command prompt with the name or address of a destination computer. The program functions by transmitting Internet Control Messaging Protocol (ICMP) Echo Request messages to the destination with gradually incremented values in the Internet Protocol header’s Time-To-Live (TTL) field. As a packet passes through routers on the way to its destination, each router reduces the TTL value by one. If the TTL value reaches 0, the last router to process the packet discards it and informs the source system of its action. Thus, the first set of Echo Request packets, which have a TTL value of 1, are discarded by the first router on the journey. The second set of packets have a TTL value of 2, and are discarded by the second router. This

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Readiness Review—Exam N10-002 process proceeds until packets reach the destination system. Using the informational messages returned by the routers, the Tracert program generates a list of the routers that the packets have passed through during the journey to their destination. Each router passed through by the request is referred to as a hop, usually limited to 30.

Ping—The Ping program, implemented as PING.EXE on Windows computers, is the most basic of TCP/IP utilities. By running Ping from the command line with the Domain Name System (DNS) name or IP address of another computer on the network, you can determine if it is possible to send TCP/IP traffic to and receive it from that computer. Ping generates ICMP Echo Request messages containing a series of random data bytes as a payload and transmits them to the specified destination. The destination computer, on receiving an Echo Request, repackages the payload in an ICMP Echo Reply message and sends it back to the source computer. The computer running Ping displays the incoming reply messages, along with their round trip travel times, TTL values, the number of data bytes in the payload, and the IP address of the destination computer. ICMP operates at the network layer of the Open Systems Interconnection (OSI) reference model, so using Ping to send messages to another computer on the network tests the entire protocol stack from the network layer down, including the network hardware. You can use Ping to determine whether the computer you are using can communicate with the network, whether another computer on the network is functioning properly, or whether intermediate systems on an internetwork, such as routers, are functioning properly. ARP—TCP/IP computers use the Address Resolution Protocol (ARP) to determine the hardware or Media Access Control (MAC) address associated with a particular IP address. At the network layer and above, TCP/IP systems use IP addresses to identify computers on a network. However, before a computer can transmit data to another computer, it must discover the hardware address of that computer, which the data-link layer protocol uses in its header. ARP uses broadcast transmissions to resolve IP addresses into hardware addresses, and stores both in memory temporarily in what is known as an ARP cache. On Windows computers, the ARP.EXE program enables you to display and manipulate the contents of the ARP cache. By running ARP.EXE from the command line with the -s parameter, followed by the IP address and hardware address of a particular computer on the network, you can add a new, permanent entry to the cache, which eliminates the need for the computer to repeatedly resolve that IP address. By eliminating the address resolution process, you can speed up the establishment of a connection between computers on a network. Netstat—Netstat, in UNIX, and NETSTAT.EXE, in Windows, are programs that display information about a TCP/IP computer’s current connections, as well as network traffic statistics for the various TCP/IP protocols. Running NETSTAT.EXE from a Windows command prompt with the -a parameter, for example, displays a list of all of the computer’s active connections to other computers on the network,

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as well as a list of the ports over which the computer is listening for incoming connections. This enables you to identify what network processes are running at the upper levels of the protocol stack, which can aid in troubleshooting communication problems that pass the Ping test. Running NETSTAT.EXE with the -s parameter displays a variety of traffic statistics about the IP, ICMP, TCP, and UDP (User Datagram Protocol) protocols, such as the number of messages received using each protocol and how many errors of various types have occurred. Netstat is not a replacement for a full-featured protocol analyzer like Windows 2000’s Network Monitor application, but it does provide quick information about network processes that can be useful in a troubleshooting situation.

Nbtstat—NBTSTAT.EXE is a Windows program that displays information about the NetBIOS over TCP/IP (NetBT) connections currently in use on the computer. Running NBTSTAT.EXE with the -c parameter displays the contents of the computer’s NetBIOS name cache, which contains the NetBIOS names that have recently been resolved into IP addresses. Other parameters display the NetBIOS names registered on the computer or on another computer on the network. You can use Nbtstat to determine if computers are resolving NetBIOS names properly and to load permanent entries in the name cache that you have added to an LMHOSTS file. By preloading the name cache, you can speed up the connection establishment process by eliminating the name resolution procedure. Ipconfig/Ifconfig/Winipcfg—UNIX operating systems typically use a program called Ifconfig to assign configuration parameters to a network interface. Running Ifconfig without any command line parameters displays the interface’s current configuration. The Windows operating systems have a similar program that displays the configuration parameters for all of the computer’s interfaces, but it omits the parameter assignment function. On Windows 2000 and Windows NT, the program runs from the command line and is called IPCONFIG.EXE. Windows 95, 98, and Me have a graphical program called WINIPCFG.EXE that performs the same functions. One of primary benefits of IPCONFIG.EXE and WINIPCFG.EXE is that they can display the IP addresses and other parameters assigned to a Windows computer by a Dynamic Host Configuration Protocol (DHCP) server. When DHCP automatically configures a Windows TCP/IP client, the assigned settings do not appear in the Control Panel’s network configuration interface, so Ipconfig and Winipcfg are the quickest means of determining what IP address and other settings the computer is using. In addition, IPCONFIG.EXE and WINIPCFG.EXE both have controls that enable you to release and renew the TCP/IP parameters currently assigned by DHCP.

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Objective 4.1 Questions N10-002.04.01.001 Which of these operating utilities is best used to determine if a router is failing to forward packets? A. Ping B. Tracert C. Ipconfig D. Nbtstat

N10-002.04.01.002 Which of the following utilities rely on the ICMP protocol to perform their functions? (Choose two.) A. Netstat B. Arp C. Tracert D. Ping

N10-002.04.01.003 Which of the following utilities can help speed up the process by which one TCP/IP computer establishes a connection to another? (Choose two.) A. ARP B. Ping C. Winipcfg D. Nbtstat

N10-002.04.01.004 A network administrator suspects that a particular computer is running an unauthorized Web server. Which of the following utilities can help the administrator determine if this is true? A. Nbtstat B. Tracert

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C. Netstat D. Ping

N10-002.04.01.005 A workstation on a local area network (LAN) is unable to access a Web page on a server located on the same LAN. To test the connection, a network support technician runs the Ping program on the workstation with the DNS name of the Web server, and Ping successfully receives replies to its Echo Request messages. Given this information, which of the following could conceivably be the cause of the problem? A. The network interface adapter on the workstation is malfunctioning. B. The DNS server on the network is down. C. The Web server is running the wrong data-link layer protocol. D. The Web server application on the target computer is not running.


Correct Answers: B A. Incorrect: Although you can use the Ping utility to determine if a router is accessible using the TCP/ IP protocols, Ping cannot determine whether the router is functioning properly by forwarding packets to other networks. B. Correct: Tracert can determine whether a router is forwarding packets properly because its function is to display a list of the routers that process packets on the way to their destination. When you use Tracert, the program transmits a series of packets that are designed to expire at each router on the path to the destination in turn. As each router receives a packet with a TTL value of 0, the router discards the packet and transmits an error message back to the sending system. If Tracert displays the name or address of a particular router in its output listing and then successfully sends packets to the next router on the path, you know for certain that the first router is forwarding packets properly. C. Incorrect: Ipconfig can display the TCP/IP configuration parameters of the computer on which it is running, but it cannot determine if the computer is successfully transmitting and receiving data, nor can it know anything about a router elsewhere on the network. D. Incorrect: Nbtstat can display information related to the NetBT function of a particular Windows computer on the network, but it has nothing to do with a router’s packet forwarding capabilities.

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N10-002.04.01.002

Correct Answers: C and D A. Incorrect: Netstat displays only information about the network traffic sent and received by the computer on which it is running. Netstat generates no network traffic of its own and does not require the use of ICMP or any other protocol. B. Incorrect: The ARP utility displays and manages the ARP cache on the computer where it is running and does not rely on ICMP or any other protocol for its functionality. C. Correct: Tracert functions by generating a series of ICMP Echo Request messages and transmitting them to the name or address specified on the command line. The capability to send and receive ICMP messages is essential for Tracert to function. D. Correct: The Ping utility relies completely on ICMP for its functionality. Ping sends ICMP Echo Request messages to the specified destination and then listens for returning Echo Reply messages.

N10-002.04.01.003

Correct Answers: A and D A. Correct: Part of the network communications process for a TCP/IP computer is the resolution of the destination IP address for each packet into a hardware address that the data-link layer protocol can use. In most cases, ARP performs this resolution by transmitting broadcast messages containing the IP address and waiting for the computer using that address to reply with a message containing its hardware address. By using the ARP.EXE utility to add a particular IP address and its associated hardware address to the ARP cache, you can eliminate this name resolution, which speeds up the connection process. B. Incorrect: Ping is a diagnostic utility that you use to determine if one computer on a TCP/IP network can communicate with another. Ping does not affect the performance of the computer’s network interface once it has finished running. C. Incorrect: The Winipcfg utility simply displays information about the computer’s current TCP/IP configuration. Winipcfg does not use or affect the network communications process. D. Correct: You can use Nbtstat to preload entries into a computer’s NetBIOS name cache. The name cache contains NetBIOS names and their equivalent IP addresses. When two computers on a Windows network communicate with each other using NetBIOS names for identification, the first step is to resolve those names into IP addresses using either broadcast messages or a Windows Internet Name Service (WINS) server. By preloading a name and address into the cache, you eliminate the need for the name resolution process. The computer can simply read the address from the cache stored in memory, which is much faster than transmitting messages over the network.

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N10-002.04.01.004

Correct Answers: C A. Incorrect: Nbtstat can display the NetBIOS names registered to a particular computer on a network, but it cannot determine if a computer is running a particular application, such as aWeb server. B. Incorrect: You can use Tracert to determine if packets are reaching a particular computer on the network. However, since Tracert uses ICMP, which is a network layer protocol, it cannot determine if an application layer process like a Web server is running on that computer. C. Correct: Netstat can list the port numbers on a computer that are in a listening state, meaning that they are awaiting incoming traffic from other computers on the network. A computer that is running a Web server has port number 80 open in a listening state, because this is the port assigned to the Hypertext Transfer Protocol (HTTP), which is the protocol thatWeb clients and servers use to communicate. D. Incorrect: Ping can determine if a particular computer on the network is running and able to receive and transmit messages, but like Tracert, Ping relies on the network layer ICMP protocol and cannot determine if a Web server is running on the computer.

N10-002.04.01.005

Correct Answers: D A. Incorrect: Ping uses the ICMP protocol at the network layer to generate its messages, so if a Ping test is successful, this means that all of the networking components at the network layer and below on the two computers involved are functioning properly. The network interface adapter functions at the physical and data-link layers, so successfully transmitting and receiving Ping test messages indicates that the network interface adapters on both computers are functioning properly. B. Incorrect: When you run the Ping utility with the DNS name of a computer on the network, the first thing the program does is resolve that name into an IP address by sending it to a DNS server. If the Ping test is successful, then the name was successfully resolved and the DNS server is functioning properly. C. Incorrect: The data-link layer of the OSI reference model is below the network layer, which is where the ICMP protocol used by Ping operates. For a Ping test to be successful, the two computers involved must be running the appropriate data-link layer protocols for the network on which they are located. Therefore, the use of the wrong data-link layer protocol cannot be the problem in this case. D. Correct: Because Ping tests only the network functionality of the two computers as high as the network layer, it is entirely possible for them to pass a Ping test and for the connection between a Web client and server to still fail. Web clients and servers are both application layer processes, and if the Web server application is not running or malfunctioning, the client cannot connect to it, despite the fact that both computers can still communicate over the network.


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4 . 2

Given a troubleshooting scenario involving a small office/home office network failure (e.g., xDSL, cable, home satellite, wireless, POTS), identify the cause of the failure.

It is increasingly common for private homes and small offices to have their own LANs instead of stand-alone computers, and one of the most common reasons for installing a small LAN is to share a single connection to the Internet among users on several computers. The task of building a home or small office network has been simplified in recent years by the proliferation of inexpensive Ethernet hardware designed for a small network environment. Inexpensive Plug and Play network interface cards (NICs), prefabricated cables, and four- to eight-port mini-hubs are available at almost every computer store these days, and a much wider selection of products is sold through catalogs and online retailers. While most home and small business networks run Ethernet over twisted pair cable, recent advances in wireless networking technology and the ratification of the 802.11b standard by the Institute of Electrical and Electronic Engineers (IEEE) have led to the rapid introduction of many inexpensive wireless networking products intended for this type of network. A wireless LAN uses one of two topologies. In the ad hoc topology, all of the computers on the network are equipped with wireless network interface adapters and communicate freely with each other. In the infrastructure topology, you connect a wireless transceiver called an access point to a standard wired network, and computers with wireless network interface adapters communicate with the wired network via the access point. Troubleshooting a home or small office LAN is relatively easy; if all of the required hardware and software components are in place, the computers should be able to communicate. However, a shared Internet connection or the use of non-standard hardware can complicate the troubleshooting process considerably. A shared Internet connection incorporates a wide area network (WAN) link into the network design and requires a

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Readiness Review—Exam N10-002 router to propagate traffic between the LAN and Internet using the WAN connection. Some of the WAN technologies most commonly used to connect a home or small business network to the Internet are as follows:

POTS—The Plain Old Telephone Service (POTS) refers to the standard dial-up telephone system, also known as the Public Switched Telephone Network (PSTN). A POTS connection with a modem at each end is the simplest and most common type of WAN connection. It is used to connect a single computer to a remote network or to connect two networks. The combination of the POTS connection, the two modems, and the interfaces that connect the modems to the computers (which are typically bus slots or serial ports) form the physical layer of the networking stack. A modem (which is an abbreviation of modulator-demodulator) converts the digital data a computer generates into analog signals that can be transmitted over the POTS line. A similar modem at the other end of the connection converts the analog signals back into digital form, so the other computer can receive them. xDSL—Digital Subscriber Line is a dedicated point-to-point communications service that uses standard telephone lines to provide high-speed, digital connections. DSL service is available in a variety of formats, which are identified by a fourth initial, such as Asymmetrical Digital Subscriber Line (ADSL) and High bit-rate Digital Subscriber Line (HDSL). Because the first initial is mutable, the service is sometimes referred to generically as xDSL. The various types of DSL service provide connections at different speeds and over different lengths. Many DSL connections are asymmetrical, meaning that they run at different speeds in each direction. For example, the ADSL service typically used to provide users with Internet access can run at speeds as high as 8.4 Mbps downstream (that is, from the Internet to the subscriber), but is limited to 640 Kbps for upstream traffic. This asymmetry is not a major problem for the typical Internet user who generates far more downstream than upstream traffic, but it is not suitable for running Web servers and other applications that require more upstream bandwidth. Cable—Many cable television (CATV) systems have begun to offer digital Internet access through their networks at speeds far greater than that of a standard dial-up connection. Like DSL, CATV connections are usually asymmetrical, and they also use a similar hardware configuration. The computer connected to the service uses a standard Ethernet NIC to attach to an external unit (which is inevitably and incorrectly called a modem—more commonly known as a cable modem—even when the entire system is digital and no analog conversions take place), and the unit is connected in turn to the CATV network using the same cable that provides the television service. A CATV connection differs from DSL in that it is not a dedicated connection. The CATV network is essentially a large LAN (or more appropriately a metropolitan area network, or MAN), and all of the users in the local area share the bandwidth it provides. As a result, the transmission speeds you achieve using a CATV connection can vary depending on segment sizes and other users’ activities,

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while DSL provides a consistent level of bandwidth. DSL is also inherently more secure than a CATV connection, and it can be used for private connections between computers or networks—not just for Internet access.

Home satellite—Some of the home satellite companies that provide television service also provide Internet access. An Internet connection using a home satellite differs from all of the other technologies discussed here, however, in that it is usually one-way. The small satellite dishes provided by these services can receive signals from satellites in orbit, but they cannot transmit to them, in most cases. (A few providers do offer two-way satellite service.) As a result, the satellite Internet service requires that you use a separate, standard POTS line for all upstream traffic, while the computer receives downstream traffic through the satellite connection. Problems establishing a connection over a WAN link can be due to the telephone service, and obviously there is nothing you can do when this is the case except call your service provider. However, before you reach this point, it’s important to make sure that fault lies in the POTS line and not in any of your hardware or software. You should use standard troubleshooting procedures to rule out all possible internal causes of the problem before you assume that the external service is at fault.

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Objective 4.2 Questions N10-002.04.02.001 A small real estate office installs a new Ethernet network with five PCs connected using 10Base-T cables and a mini-hub. The network’s users access the Internet using a cable modem connected to one of the computers, which is running Windows Internet Connection sharing (ICS). Immediately following the network installation, the computers were able to access each other’s shared files and printers, and the computer equipped with the cable modem was able to access the Internet. However, the other four computers were not able to access the Internet. Which of the following could possibly be the cause of the problem? A. The network cable connecting the ICS computer to the hub is faulty. B. The cable modem is malfunctioning. C. The hub’s power supply is unplugged. D. The four malfunctioning computers are using the wrong default gateway address.

N10-002.04.02.002 Which of the following statements describes a WAN technology that is asymmetrical? A. A service in which traffic runs in one direction only, such as a home satellite connection B. A service in which traffic runs faster in one direction than the other C. A service that can run at multiple speeds D. A service that runs at only one speed

N10-002.04.02.003 Which of the following WAN technologies can you use to connect two private networks together directly? (Choose two.) A. POTS B. xDSL C. Cable D. Home satellite

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Correct Answers: D A. Incorrect: If the cable connecting the computer running ICS was faulty, it would not be possible for that computer to participate on the network in any way. This means that it could not access shared resources on the other computers, nor could the other computers share its resources. B. Incorrect: If the cable modem was malfunctioning, none of the computers would be able to access the Internet, including the computer running ICS. C. Incorrect: If the hub was not functioning, there would be no communications between any of the computers on the network. The computer with the cable modem would still be able to access the Internet (because the hub is not involved), but the other computers would not be able to access each others’ shared resources. D. Correct: For computers to access a shared Internet connection, they must be configured to use the router connecting the network to the Internet as their default gateway address. In this case, the computer with the cable modem that is running ICS is functioning as the router, and the other four computers must have that computer’s IP address as their default gateway. Incorrect default gateway addresses on those four computers could explain their inability to access the Internet.

N10-002.04.02.002

Correct Answers: B A. Incorrect: It is true that a home satellite connection provides only downstream traffic from the Internet, this is generally not what is understood to be an asymmetrical service. B. Correct: An asymmetrical WAN service is one in which the upstream and downstream traffic runs at different speeds. In general, an asymmetrical service that is used for Internet connectivity provides much faster transmission speeds from the Internet to the client than from the client to the Internet. C. Incorrect: Asymmetry refers to a service that runs upstream and downstream at two different speeds simultaneously, not one that runs at a single, variable speed in both directions. D. Incorrect: An asymmetrical service always runs at a different speed in each direction.

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N10-002.04.02.003

Correct Answers: A and B A. Correct: POTS lines are all but universally available and require only a modem at each end to form a connection. As a result, you can use a POTS line to connect two computers or networks at virtually any locations, forming a WAN. B. Correct: xDSL connection uses standard telephone lines, which makes it possible to connect networks at almost any two locations. The hardware required for an xDSL connection is more complicated and expensive than dial-up modems, but it’s still possible to use xDSL to build a privateWAN. C. Incorrect: CATV networks are privately owned by cable television companies, and are used only to provide subscribers with television service and Internet access. You cannot use a CATV network connection as a WAN link between two private networks. D. Incorrect: Like CATV networks, the satellite networks that provide Internet access are privately owned, and you cannot use them to connect two private networks together. In addition, the one-way transmissions home satellite dishes usually provide would make this medium impractical for such an application.

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4 . 3

Given a troubleshooting scenario involving a remote connectivity problem (e.g., authentication failure, protocol configuration, physical connectivity), identify the cause of the problem.

A remote network connection can fail for a variety of reasons, and as with any networking problem, the troubleshooting process consists of eliminating possible causes until you find the one preventing the connection. In remote networking, three of the most common areas where a failure to connect can occur are as follows:

Physical connectivity—A remote network connection can use any one of many different WAN technologies to create the physical connection between the computer and the network. In virtually all cases, the WAN link involves an outside service provider, such as a telephone company, so it’s possible for a physical connectivity problem to be caused by a malfunction either in the provider’s service or in the connection of the computers to the service. For example, in the case of a remote network connection using a standard POTS line, a physical connection failure can be caused by a problem with the modem or its interface to the computer, or there can be a malfunction in the telephone line. In the latter case, only the telephone service provider can resolve the problem (unless you use a different POTS line). Before assuming that the POTS line is at fault, you should begin troubleshooting by checking the physical components of the connection that are under your control, such as the cable connecting the modem to the telephone line and the interface between the modem and the computer. An internal modem can be improperly seated in the bus slot, and an external modem could be connected to the computer’s serial port with a faulty cable. A physical connectivity problem can also be caused by the device driver or other software that enables the computer to communicate with the connection hardware. Different WAN technologies involve different hardware components, some of which you may not be able to service yourself. For

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Readiness Review—Exam N10-002 example, if you suspect a faulty modem is causing the connection problem, you might be able to try replacing it with another. However, if you know the WAN connection is a T-1 leased line, you are far less likely to have an extra CSU/DSU (channel service unit/data service unit) available.

Protocol configuration—For a computer to connect to a remote network, it must be running the same protocols as that network, and those protocols must be configured properly. In some cases, you can determine that the computer is connecting physically, but that a problem is occurring later in the connection establishment process. At the data-link layer of the Open Systems Interconnection (OSI) reference model, the two computers involved in the connection generally run either the Serial Line Internet Protocol (SLIP) or, more commonly these days, the Pointto-Point Protocol (PPP). SLIP is a minimal protocol that provides only basic communication service, while PPP is newer and provides a variety of different connection options, including support for multiple protocols at the network layer and for multiple authentication protocols.To establish a remote network connection, the client computer must be configured to use a protocol that is supported by the server to which it will connect. Many remote access servers can support both SLIP and PPP connections, but it’s possible that the server you’re trying to connect to supports only one of the two, and you must configure the client to use that protocol. Using the appropriate data-link layer protocol is enough to establish a connection with a remote access server, but in order to access its resources and those of the network, the client must also be configured to use the same network layer protocol. Most remote network access connections use the TCP/IP protocols, but it is also possible to use the Novell NetWare IPX (Internetwork Packet Exchange) or NetBEUI (NetBIOS Extended User Interface) protocols. The use of PPP at the data-link layer enables the client computer to negotiate the use of one or more common network layer protocols during the connection establishment process. IPX and NetBEUI don’t require any special configuration, but when using TCP/IP, the client’s network interface must be configured to use settings that are appropriate for the remote network, such as an IP address, subnet mask, and DNS server addresses. In most cases, the remote access server assigns an IP address and other settings to the client, but it may be necessary to configure the client manually before communication is possible. Authentication failure—Most remote access connections are secured by using an authentication protocol, and even when both computers are configured correctly, the connection can fail due to an improper authentication sequence. PPP enables the client and server computers to negotiate the use of a common authentication protocol. The simplest of the authentication protocols in general use is the Password Authentication Protocol (PAP). PAP uses a simple two-way handshake

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authentication sequence in which the client transmits an account name and password to the server and the server allows or denies the client access. PAP is relatively insecure because it transmits the name and password in clear text, which can conceivably be intercepted. One of the more secure authentication protocols is the Challenge Handshake Authentication Protocol (CHAP). CHAP uses a threeway handshake and never transmits account names and passwords in clear text. For the authentication process to succeed, both the client and the server must have at least one authentication protocol in common. During the PPP negotiation, the computers exchange information about the protocols they support and agree on one to use. If an authentication failure occurs during the connection establishment process, it could be because the server requires the use of an authentication protocol that the client does not support. Of course, supplying an incorrect account name and/or password also causes an authentication failure, whichever protocol is in use.

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Objective 4.3 Questions N10-002.04.03.001 Which of the following statements best describes the difference between SLIP and PPP? A. PPP runs at higher speeds than SLIP. B. SLIP provides support for various authentication protocols, and PPP does not. C. SLIP requires the use of the TCP/IP protocols at the network layer, but PPP can use any network layer protocol. D. PPP is a newer, more advanced protocol than SLIP.

N10-002.04.03.002 While attempting to configure a standalone computer to access a remote network using a POTS line and a modem, you experience repeated connection failures. Which of the following troubleshooting steps would not help you determine if a physical connectivity problem is preventing a remote network connection? A. Replace the cable connecting the modem to the telephone jack. B. Call the telephone company to have the line checked. C. Check the computer’s IP address. D. Check the computer’s modem configuration.

N10-002.04.03.003 Which of the following additional protocols must you have installed on a remote network client computer to access a server that requires the use of CHAP? A. TCP/IP B. PPP C. IPX D. SLIP

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Correct Answers: D A. Incorrect: Both SLIP and PPP are data-link layer protocols that operate independently of the physical layer, and therefore have no effect on the speed of the connection. B. Incorrect: SLIP is a simple protocol that provides no support for configuration options or ancillary protocols, and PPP enables the client and server to negotiate a common authentication protocol, among other parameters. C. Incorrect: Both SLIP and PPP can operate with any network layer protocol, including TCP/IP. The difference between the two is that PPP supports the use of multiple network layer protocols at the same time, and SLIP does not. D. Correct: PPP was created after SLIP to provide a more robust and configurable protocol for WAN connections at the data-link layer.

N10-002.04.03.002

Correct Answers: C A. Incorrect: A faulty cable can cause a physical connectivity failure that prevents a client computer from establishing a connection to a remote access server. Replacing the cable with one that definitely works eliminates this as a possible cause of the problem. B. Incorrect: A physical connectivity problem in a remote access connection can conceivably be caused by a malfunction in the equipment of the service provider supplying theWAN link. Only the provider can troubleshoot this equipment, so contacting it is one way of eliminating the telephone line as a possible cause of the problem. C. Correct: The IP address is part of the client computer’s TCP/IP configuration and has no relationship to the physical connection. While an incorrect IP address can cause the connection to fail, checking it is not a means of verifying the physical connectivity. D. Incorrect: It is possible for a modem connection to fail despite the modem and its physical connections to the computer and the telephone line to be in working order. The computer must be configured to send the appropriate commands to the modem for the client to establish a physical connection to the server, so checking this configuration is still a means of verifying the client’s capability to physically connect to the server.

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N10-002.04.03.003

Correct Answers: B A. Incorrect: The TCP/IP protocols operate primarily at the network layer of the OSI model and above, while the use of an authentication protocol is part of the PPP connection establishment, which is a data-link layer process. You can therefore use CHAP for the client authentication with any network layer protocol. B. Correct: SLIP does not provide the capability for a client and a server to negotiate the use of an authentication protocol like CHAP. PPP is required for this negotiation and must be supported by both the client and the server for CHAP to be used. C. Incorrect: IPX is also a network layer protocol and has no relationship to the data-link layer process of negotiating and using an authentication protocol like CHAP. D. Incorrect: SLIP provides only basic connectivity between a client and a server and does not provide support for authentication protocols such as CHAP.

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4 . 4

Given specific parameters, configure a client to connect to the following servers: UNIX/ Linux, NetWare, Windows, Macintosh.

With today’s operating systems and protocols, virtually any client computer can connect to any server and access services such as shared files, printers, and applications. However, the process of configuring the client to access a particular type of server can vary, depending on the operating systems involved. Most of the client workstations on existing networks run some form of Windows, but servers can run any one of the following operating systems:

UNIX/Linux—The UNIX and Linux operating systems rely exclusively on the TCP/IP protocols, so all clients must support TCP/IP to access a UNIX or Linux server. Configuring a TCP/IP client is a matter of assigning it an IP address that is unique on the network and a subnet mask. Depending on whether an internetwork or an Internet connection is involved, you may also have to supply a default gateway address and DNS server addresses. UNIX and Linux computers generally also have a host name that simplifies the process of identifying them and use either a HOSTS file or a DNS server to resolve the host names into the IP addresses used for TCP/IP communications. If you are connecting to a UNIX/Linux server with a UNIX/Linux client, this configuration is typically all that is needed. When connecting to a UNIX/Linux server with a Windows client, the TCP/IP configuration alone enables you to access UNIX/Linux server applications such as FTP and Telnet, but you cannot access the file system or printers on a UNIX/Linux server using just TCP/IP. Most UNIX and Linux servers share their files using the Network File System (NFS) and their printers using the lpd (line printer daemon) program, so a Windows computer has NFS and lpr (line printer remote) client applications to access the server resources. Windows 2000 includes an lpr implementation, but you must install the Microsoft Services for UNIX product to access NFS file systems. NetWare—Novell NetWare, version 5, supports both the traditional Internetwork Packet Exchange (IPX) protocols and TCP/IP. To connect to a NetWare server

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Readiness Review—Exam N10-002 using TCP/IP, you need the standard configuration parameters, but IPX requires no configuration. The NetWare operating system includes client software for the various Windows operating systems, and Windows also includes its own NetWare clients. You must install either the Microsoft or Novell client for NetWare on a Windows computer to access NetWare server resources. For Macintosh and UNIX clients to access NetWare server, additional software is required. Because NetWare is strictly a client/server operating system, there is no direct communication between NetWare clients, and therefore, there is no need for them to be assigned names, as NetWare servers are. To connect to a NetWare network, you specify a preferred server or a Novell Directory Services (NDS) tree name in the client software.

Windows—When you install any one of the Windows operating systems on a computer, you must specify a computer name for it. This name is actually a NetBIOS name, which Windows uses to identify the computer on the network. When the network is running the NetBEUI protocol, the NetBIOS name is the only identifier each computer has, and no further protocol configuration is needed. If the network is running TCP/IP, you must also assign an IP address to the computer, as well as the other standard TCP/IP configuration parameters. The computers typically use the WINS or broadcast transmissions to resolve NetBIOS names into their equivalent IP addresses. In addition to the protocol module, a Windows computer must also have the Client for Microsoft Networks and a network interface adapter driver installed to access Windows network servers. UNIX, Linux, and Macintosh clients can access Windows TCP/IP server applications without any additional software, but to access shared files and printers on Windows servers, you must install Microsoft Services for UNIX or Microsoft Services for Macintosh on the Windows servers. Macintosh—Macintosh computers are not often used as servers on heterogeneous networks. In most cases, only all-Macintosh networks use them. The original Macintosh networking capability centered around the AppleTalk protocols, which are included with the Macintosh operating system. At the data-link layer, a proprietary protocol called LocalTalk provided connectivity using an interface built into Macintoshs. To configure a client to access a Macintosh server, it had to support AppleTalk. Today, Macintosh computers use TCP/IP as their default networking protocols, and Macintosh versions of the Ethernet and Token Ring data-link layer protocols, called EtherTalk and TokenTalk, enable Macintosh computers to connect to standard LANs.

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Objective 4.4 Questions N10-002.04.04.001 Which of the following TCP/IP configuration parameters are not required to connect a client workstation to a LAN? (Choose two.) A. An IP address B. A subnet mask C. A DNS server address D. A default gateway address

N10-002.04.04.002 Which of the following server operating systems cannot use names to identify clients on the network? A. Microsoft Windows 2000 B. Novell NetWare C. UNIX/Linux D. Macintosh

N10-002.04.04.003 What is the name of the software module that client computers use to access a UNIX printer? A. NFS B. lpr C. lpd D. HOSTS

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N10-002.04.04.004 Which of the following server operating systems can share its file system with a Windows client using only the software supplied with the Windows 2000 operating system? (Choose two.) A. UNIX B. Windows C. NetWare D. Macintosh


Correct Answers: C and D A. Incorrect: Every computer on a TCP/IP network must have a unique IP address assigned to it, either manually or through an automatic service like the DHCP. B. Incorrect: The subnet mask specifies which bits in the IP address identify the network on which the computer resides and which bits identify the computer, and it is a required element of the TCP/IP configuration. C. Correct: Clients use DNS servers to resolve host names into the IP addresses needed for TCP/IP communications, especially when accessing the Internet. However, most LANs do not use host names to identify computers, so the use of a DNS server is not strictly required. D. Correct: The default gateway address identifies the router that the client uses to send traffic to computers on other networks. When connecting a client to a single LAN, no routing is needed, so there is no need to configure a default gateway address.

N10-002.04.04.002

Correct Answers: B A. Incorrect: All Windows computers must be assigned a NetBIOS name during the operating system installation. The computers use these names when browsing and accessing network resources. B. Correct: NetWare servers never have a reason to identify clients by name, because NetWare communications are strictly client/server and the clients always initiate the communication with the server. Since NetWare clients cannot communicate with other clients, there is no reason for them to have names.

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C. Incorrect: UNIX and Linux servers can use host names to identify computers on the network, resolving them into IP addresses with either a DNS server or a HOSTS file. D. Incorrect: Macintosh networks use names to identify specific computers; groups of computers on a Macintosh network are called zones.

N10-002.04.04.003

Correct Answers: B A. Incorrect: The NFS is a client/server application that enables computers to share and access shared file systems over the network. NFS does not provide printing capabilities. B. Correct: Lpr is the client printer program that communicates with the lpd printing program running on a server. Most UNIX and Linux operating systems use these programs for sharing printers with a network. C. Incorrect: Lpd is the server program most UNIX and Linux operating systems use to share printers with network clients. Lpr is the client program that sends print jobs to lpd, running on another computer. D. Incorrect: A HOSTS file is nothing more than a list of host names and their equivalent IP addresses that TCP/IP computers can use to resolve the names supplied to applications into the addresses needed for TCP/IP communication. The HOSTS file has nothing to do with the network printing process.

N10-002.04.04.004

Correct Answers: B and C A. Incorrect: A Windows client cannot access a UNIX server without additional software. Most UNIX operating systems use NFS to share files, and Windows 2000 does not include NFS client software. You must buy and install Microsoft Services for UNIX to access NFS on a UNIX server. B. Correct: Windows 2000 includes all the client software you need to access files on any other Windows computer on the network. This software consists of the Client for Microsoft Networks module, plus protocol modules and network interface adapter drivers. C. Correct: Despite the fact that Novell NetWare includes client software for Windows, you can access NetWare servers with the Windows 2000 operating system only because Microsoft supplies its own NetWare client as well. To access a NetWare server, you install the Client for NetWare Networks, plus a network interface adapter driver and either the IPX or TCP/IP protocol module. D. Incorrect: Windows 2000 includes Microsoft Services for Macintosh with the operating system, but this package only enables Macintosh clients to store their files on Windows servers only. Services for Macintosh does not enable Windows computers to access files on a Macintosh server.


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O B J E C T I V E

4 . 5

Given a wiring task, select the appropriate tool (e.g., wire crimper, media tester/certifier, punch down tool, tone generator, optical tester, etc.).

Installing network cables is a specialized task that most network administrators outsource to an external contractor. However, it is important for people who are responsible for maintaining and supporting the network to have an understanding of how the cable system works and of the specialized tools used to install and troubleshoot network cables. Using these tools, you may be able to isolate the location of a cabling problem, and, even if you don’t repair it yourself, save the time of a repairperson who charges by the hour. Some of the tools used in cable installation and testing processes are as follows:

Wire crimper—A wire crimper is a device that looks like a large pair of pliers with jaws that are specially designed to grasp the components of a cable connector. You use a crimper to attach connectors to a length of bulk copper cable. Although the network cables you can buy in a computer store are usually prefabricated (with connectors attached at both ends), professional cable installers work with large spools of bulk cable so they can cut off the length they need and attach the appropriate connectors. Installers use a crimper to attach the connectors needed to make patch cables, which connect wall plates to computers and patch panel ports to hubs. Connecting the bulk cable to the wall plates and patch panels requires different tools. The connector is supplied in pieces.To attach a connector to a cable, you strip the insulation off the cable, lay the wires in the connector parts, and squeeze them together using the crimper. The details of the procedure differ depending on the cable and connector types you use. You can buy a crimper and some loose connectors yourself and make your own patch cables, but be aware that learning to attach the connectors properly requires a good bit of practice, and the process is rather time consuming. Buying prefabricated patch cables may be the more economical choice.

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Media tester/certifier—A media tester or media certifier is an electronic device (usually handheld) that performs a variety of tests on an installed cable run, compares the results with standards programmed into the unit, and displays the results in the form of pass/fail readouts for each test. The number and type of tests differ depending on the unit, but typically include tests for basic wiring faults, such as shorts, open circuits, and transposed wire pairs, as well as cable length, attenuation (the weakening of a signal as it travels over a length of cable), and various types of crosstalk (signal bleedover to adjacent wires). Media testers and certifiers can range up to several thousand dollars. The more elaborate units typically perform more tests (which you may or may not need, depending on the type of network you’re running), and may include additional features, such as a printer or additional memory for storing results. When using media testers, it’s important to understand that the pass/fail test results are only as accurate as the standards programmed into the device. These official standards for cable performance may change over time, which is why you can change the standards on some of these products as needed. However, you should also be aware that it is a simple matter for an unscrupulous cable installer to modify the standards programmed into a media tester so that an improperly installed cable passes all of the tests. Before using a media tester, you should make an effort to learn what the raw test results provided by the device mean, rather than simply relying on the pass/fail reading. Punch down tool—A punch down tool is a device for connecting the ends of bulk cables to wall plates and patch panel ports. In a professional cable installation, you pull lengths of bulk cable through walls and ceilings, and then attach one end to the connector in a wall plate located near the computer and the other end to a patch panel near the network hub. A patch panel is simply a group of connectors mounted in a frame, which functions as the cabling nexus for the entire network. For a network using twisted pair cables, the process of attaching the cable end to the connector in the wall plate patch panel is called punching down.To punch a cable down, you have to cut back some of the cable sheath, untwist the individual wire pairs inside the cable, lay the wires out in the appropriate slots in the connector, push each wire down into the connector slot, and trim off the ends. Because a typical network cable contains eight wires, this process can be labor intensive and time consuming. However, a punch down tool simplifies the process by performing the last two steps at once. Once you lay the wires in place on the connector, you push down on each one with the tool, which sets and trims it all in one step. Tone generator—A tone generator is a simple cable testing device that actually consists of two units, the tone generator and a locator that detects the tone. This type of tester is sometimes called a “fox and hound” wire tracer. The tone generator is an electrical device that typically has both a standard cable jack and an alligator clip. You plug a cable into the jack or connect the clip to a single wire inside a cable and the device transmits a signal over it. The locator has a probe on it that you touch to the cable or wire at the other end, which causes it to emit an audible tone.

Objective 4.5

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You can use this type of device to test an installed cable for many of the usual problems a faulty installation causes. For example, if you clip the generator to a connector pin at one end of the cable and touch the probe to the corresponding pin at the other end and it does not produce a tone, you know you have a problem. Further probing can determine if the problem is an open circuit (no connection to the other end of the cable), a transposed wire pair (the wires are connected to the wrong pins at the other end), a short (a break in the wire detected by probing along its length), or some other problem. The tone generator is a simple and inexpensive tool that is good for occasional testing and troubleshooting, but using it can be extremely time consuming. To verify that a twisted pair cable is installed properly, you must test each of the eight wires individually. You must also have either two people working in cooperation at the two ends of the cable or the time and energy to run back and forth as you fix the tone generator at one end and then probe for the tone at the other. Professional installers typically use another testing device, such as a wire map tester (which uses the same principle as the tone generator and locator but tests all eight wires at once for all of the basic cabling faults) or a media tester/ certifier.

Optical tester—The installation and testing tools listed so far are all for use on networks that use copper cable. Fiber optic networks operate on a completely different principle and require different types of equipment. Because fiber optic cables carry light impulses instead of electrical charges, the test equipment generally consists of a light source for one end of the cable and a light sensor for the other end. The basic testing technique of generating a signal at one end of the cable and detecting it at the other is the same as in a copper cable network, but many of the attributes that the devices test are different. One of the basic tools for testing fiber optic connections is called an optical loss test set (OLTS) or fiber optic test kit, which consists of a power meter and a test source. The test source generates a precisely calibrated beam of light at one end of the cable, while the power meter reads the signal’s intensity at the other end. This testing capability is also available as part of multifunction media tester/certifier units that operate much like the ones used for copper cables. You connect the device to the cable and it provides pass/fail results for a series of tests pertinent to fiber optic networks, including optical power and signal loss (attenuation). Optical testers of this type can be even more expensive than their copper cable counterparts, with top-of-the-line models costing $5,000 or more. An even higher-end fiber optic testing device is the optical time domain reflectometer (OTDR), which can locate many different types of cable breaks and manufacturing faults on fiber optic cable connections. OTDRs require extensive training and practice to use effectively and can cost as much as $30,000.

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Objective 4.5 Questions N10-002.04.05.001 Which of the following implements do you use while connecting a wall plate to a patch panel? A. A crimper B. A prefabricated patch cable C. A punch down tool D. A media tester/certifier

N10-002.04.05.002 Which of the following tools can you use to detect an open circuit on a twisted pair cable installation? (Choose two.) A. A fox and hound tester B. An OTDR C. A wire map tester D. An OLTS

N10-002.04.05.003 Which of the following procedures does a punch down tool not perform? A. Trimming of the wire ends B. Untwisting the wire pairs C. Pierce the insulation at the wire ends D. Pushing the wires into the connector slots

Objective 4.5

223

N10-002.04.05.004 Which of the following tools can only test a twisted pair cable connection for wiring faults one wire at a time? A. A tone generator and locator B. A wire map tester C. A media tester/certifier D. An OLTS


Correct Answers: C A. Incorrect: A crimper is a device you use to attach connectors to bulk cable to make the patch cables used to connect wall plates to computers and patch panels to hubs. You do not use a crimper for the internal wall plate to patch panel connection. B. Incorrect: The connection between a wall plate and a patch panel typically runs inside walls or ceilings and uses bulk cable that you attach to connectors built into the plate and panel. You do not use prefabricated patch cables for this purpose. C. Correct: You use a punch down tool to connect the bulk cable that you run within walls and ceilings to permanent fixtures at each end of the cable run, such as wall plates and patch panels. D. Incorrect: You can use a media tester/certifier after the cable is connected to verify that the installation was performed properly, but there is no need for the tester/certifier during the actual connection process.

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N10-002.04.05.002

Correct Answers: A and C A. Correct: A fox and hound tester is another name for a tone generator and locator, which are tools that you can use to test the individual wire connections within a twisted pair cable. Although this tester is not the most efficient method of testing a cable installation, it will detect an open circuit. B. Incorrect: An OTDR is a high-end tool for testing fiber optic cable installations only. You cannot use it to test copper media such as twisted pair cables. C. Correct: A wire map tester can detect an open circuit on a twisted pair cable and is far more efficient and easier to use than a fox and hound tester. By connecting the two parts of the wire map tester to opposite ends of the cable, the unit tests all eight wire connections simultaneously for a variety of faults. D. Incorrect: An OLTS is a tool for fiber optic cable testing; it can’t be used to test twisted pair cables.

N10-002.04.05.003

Correct Answers: B A. Incorrect: The last action of the punch down tool after setting the wire into the connector slot is to cut off the loose end of the wire protruding past the slot. B. Correct: The punch down tool does not untwist the wire pairs. You must do this manually and line up each wire with the appropriate slot in the connector. C. Incorrect: As the punch down tool presses a wire into the connection contacts, it pierces the insulation on the wire, so that the copper conductor inside can make an electrical contact with the conductor in the connector slot. D. Incorrect: After stripping the wire, the punch down tool presses the bare copper conductor into the connector slot in order to make an electrical contact.

N10-002.04.05.004

Correct Answers: A A. Correct: To test a cable using a tone generator and locator, connect the tone generator to each cable wire in turn, and use the locator to detect the signal on each wire before proceeding to the next one. B. Incorrect: A wire map tester transmits test signals over all of the wires in the cable at the same time and reads the signals at the other end simultaneously. C. Incorrect: A media tester/certifier incorporates wire map testing into its functions, enabling it to test all of the wire connections in a cable at the same time. D. Incorrect: An OLTS is a testing device that cannot be used to test twisted pair cable connections.

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O B J E C T I V E

4 . 6

Given a network scenario, interpret visual indicators (e.g., link lights, collision lights, etc.) to determine the nature of the problem.

Troubleshooting a networking problem can often be difficult, but there are some hardware components used on networks that provide visual indicators of their status, such as light emitting diodes (LEDs), which can aid in the troubleshooting process. Understanding the exact significance of these indicators is important if you’re going to use them effectively. The most basic type of indicator is the power light found on most networking equipment. Technical people looking for the cause of a problem sometimes tend to neglect the simplest solutions. When network communications fail, the cause can often be something as simple as the power plug to a hub, router, or other device being knocked out. When a networking problem occurs, it’s a good idea to check the simplest causes first, before you move on to the more complicated ones. Familiarizing yourself with your equipment’s normal LED displays can sometimes enable you to tell at a glance if they’re functioning. Another useful indicator of network status is the link pulse LED found on most Ethernet network interface adapters and hubs that use unshielded twisted pair (UTP) cable. The link pulse LED is a tiny light located next to the RJ-45 jack on the back of the network interface adapter where it protrudes through the back of the computer. A hub typically has a row of LEDs with one representing each of its ports. The link pulse LEDs on both the network adapter and the corresponding hub port light up when the adapter is properly connected to a hub with a cable and both the hub and computer are powered up. The link pulse LED is triggered by a signal generated at the other end of the cable connection. On 10Base-T equipment, the signal is called a Normal Link Pulse (NLP). Both the network interface adapter and the hub generate a two millisecond NLP signal every 16.8 milliseconds and transmit it out to the other device. Upon receiving the signal, the device at the other end of the cable lights its LED. To determine if a connection is functioning properly, you should check to see that the LEDs at both ends are lit.

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Readiness Review—Exam N10-002 Fast Ethernet and Gigabit Ethernet equipment generates a signal called a Fast Link Pulse (FLP), which differs from the NLP signal in that it includes a link code word that specifies the transmission speeds supported by the device. Devices capable of multiple transmission speeds use this signal to automatically negotiate the fastest speed at which they can both operate. However, the signal still provides the same link pulse capability as NLP. In some cases, network adapters and hubs have a second LED used to indicate the speed at which the device is running. Do not confuse this LED with the link pulse LED, usually right next to it. It’s important to understand that the link pulse LEDs operate whenever the two devices are connected and powered. The network interface adapter should send its link pulse signal to the hub despite the computer not having a network interface adapter driver, or for that matter, even an operating system, installed. If the link pulse LEDs on one or both devices fail to light, the problem could be a faulty cable, the improper use of a crossover cable, or a lack of power to one of the devices. In addition to link pulse LEDs, many Ethernet hubs also have a collision LED that indicates when a data collision is occurring on the network. Data collisions are a normal and expected part of Ethernet communications, so seeing the collision LED light up is usually not an indication of a serious problem. However, you can use the collision LED as a quick and dirty indicator of how much traffic there is on your network. As traffic levels increase on an Ethernet network, the number of collisions increases as well. Every time a collision occurs, the computers involved must retransmit their data, thus decreasing the network’s efficiency. If you begin to see the collision LED lighting up more frequently, it could be an indication that traffic is increasing. If the collision LED spends more time lit than not, you may want to think about splitting the LAN in two using a bridge or router or installing a switch to reduce the number of collisions and improve network efficiency.

Objective 4.6

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Objective 4.6 Questions N10-002.04.06.001 When connecting a new computer to a 10Base-T Ethernet network, you plug a cable attached to a hub into the network interface adapter and notice that the link pulse LEDs do not light on either the hub or the adapter. Which of the following conditions could be a cause of the problem? (Choose two.) A. The network adapter is connected to the hub using a crossover cable instead of a straight-through cable. B. The computer does not have a network interface adapter driver installed. C. The hub is not connected to a power source. D. The computer is running the wrong operating system.

N10-002.04.06.002 How does the NLP signal differ from the FLP signal? A. The NLP signal provides connection verification only, and the FLP signal provides only autonegotiation of transmission speed. B. The FLP signal provides connection verification only, and the NLP signal provides only autonegotiation of transmission speed. C. The FLP signal provides connection verification only, and the NLP signal provides both connection verification and autonegotiation of transmission speed. D. The NLP signal provides connection verification only, and the FLP signal provides both connection verification and autonegotiation of transmission speed.

N10-002.04.06.003 Which of the following actions should you consider taking when the collision LED on your hub lights up with increasing frequency? (Choose two.) A. Installing another hub B. Installing a bridge C. Replacing the hub with a router D. Replacing the hub with a switch

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N10-002.04.06.004 After connecting a Fast Ethernet computer to a 10Base-T hub that has other computers connected to it and operating, you turn on the computer and the link pulse LED on the network interface adapter lights up, but the one on the hub does not. Which of the following could be the cause of the problem? A. The cable connecting the network interface adapter to the hub is faulty. B. The power plug for the hub is disconnected. C. The network interface adapter uses FLP signals and the hub uses NLP, and the two are not compatible. D. The computer and the hub are connected using a crossover cable.


Correct Answers: A and C A. Correct: Connecting the devices with a crossover cable would cause the transmit pins at both ends of the cable to be connected to the transmit pins at the other end. This would prevent the NLP signals from reaching the devices at both ends of the connection, preventing the LEDs from lighting. B. Incorrect: The generation of NLP or FLP signals by a network interface adapter is a process that is performed by the adapter hardware alone, without the need for an adapter driver. C. Correct: The lack of power to the hub would prevent its LED from lighting and would also prevent the hub from generating the NLP signal needed to light the LED on the network interface adapter. D. Incorrect: The generation of NLP or FLP signals by a network interface adapter is a process that is performed by the adapter hardware alone, without the participation of the computer’s operating system.

Objective 4.6

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N10-002.04.06.002

Correct Answers: D A. Incorrect: While it is true that NLP provides only connection verification, the FLP signal provides both connection verification and autonegotiation. B. Incorrect: The FLP signal provides both connection verification and autonegotiation, and NLP provides only connection verification. C. Incorrect: The NLP signal provides connection verification only, and the FLP signal provides both connection verification and autonegotiation. D. Correct: The only function of NLP signals is to light the link pulse LED on the device at the other end of the connection. FLP signals provide the same link pulse function, but also enable the devices to exchange information about the speeds at which they are capable of operating.

N10-002.04.06.003

Correct Answers: B and D A. Incorrect: Adding another hub does nothing to reduce the amount of traffic on the network, and will not reduce the number of collisions that are occurring. B. Correct: Adding a bridge splits the network into two segments and filters the traffic passing between them. The result is a reduction in the number of collisions occurring on the network and an increase in overall network efficiency. C. Incorrect: A router connects two networks, and a hub joins many computers into a LAN. Splitting one network into two and connecting them with a router would decrease the number of collisions, but you cannot simply replace a hub with a router. D. Correct: A hub forwards incoming traffic out through all of its other ports simultaneously, and a switch forwards incoming traffic only to the port providing access to the destination computer. Because packets are transmitted to the destination computer only, and not to all of the computers on the network, collisions are greatly reduced.

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N10-002.04.06.004

Correct Answers: A A. Correct: The fact that one link pulse LED is lit and the other is not indicates that the NLP/FLP signals are getting through in one direction but not the other. A faulty cable that has one or more broken wires inside the sheath could produce this malfunction. B. Incorrect: If the hub was unplugged from the power source, neither link pulse LED would light because the hub could neither generate an NLP signal nor light up its own LED. In addition, the fact that other computers are connected to the hub and operating properly indicates that it is properly connected to a power source. C. Incorrect: FLP and NLP signals are completely compatible. When a Fast Ethernet device receives an NLP signal, it interprets the lack of a link code word as an indication that the device is capable of standard Ethernet speed (10 Mbps) only. The link pulse portion of the FLP and NLP signals are identical, so this cannot be the cause of the LED failure. D. Incorrect: If the two devices were connected with a crossover cable, neither of the link pulse LEDs would light up because the NLP/FLP signals from both sides would not reach the other device. Therefore, this cannot be the cause of the problem.

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O B J E C T I V E

4 . 7

Given output from a diagnostic utility (e.g., Tracert, Ping, Ipconfig, etc.), identify the utility and interpret the output.

The standard utilities included with the TCP/IP protocol in Windows and most other operating systems have a number of different uses in the troubleshooting process, and learning to recognize and interpret their output is an important part of using the tools correctly. The output from the Ping program when you run it with the DNS name of a computer on the command line appears as follows: Pinging www.abccorp.com [64.225.87.16] with 32 bytes of data: Reply from 64.225.87.16: bytes=32 time=170ms TTL=113 Reply from 64.225.87.16: bytes=32 time=181ms TTL=113 Reply from 64.225.87.16: bytes=32 time=150ms TTL=113 Reply from 64.225.87.16: bytes=32 time=161ms TTL=113 Ping statistics for 64.225.87.16: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 150ms, Maximum = 181ms, Average = 165ms

The first line of the output contains the results of the name resolution process the Ping program performs as the first step in its process. Using Ping is a quick way to resolve a name into an IP address. Each of the following four lines contains the results of a separate transaction with the destination computer using ICMP Echo Request and Echo Reply messages. The successful receipt of replies from the destination computer in a timely matter indicates that the two systems and the network are operating properly, at least as high as the network layer of the protocol stack. Failure to receive replies from the destination computer results in Request Timed Out messages instead. Following the reply messages, Ping displays a summary of its activity, including the number of ICMP messages sent and received and the minimum, maximum, and average times between the transmission of the Echo Request message and the receipt of the Echo Reply.

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Readiness Review—Exam N10-002 The Tracert command on a Windows computer (which is called Traceroute on UNIX), produces an output like the following: Tracing route to www.abccorp.com [64.225.87.16] over a maximum of 30 hops: 1

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