CISCO NETWORKING · MCITP Certification and Beyond (Exams 70-685 and 70-686). He is currently...

CISCO NETWORKINGESSENTIALS

CISCO NETWORKINGESSENTIALS

Troy McMil lan

Acquisitions Editor: Agatha KimDevelopment Editor: Kelly TalbotTechnical Editor: Leslie HerronProduction Editor: Eric CharbonneauCopy Editor: Sharon WilkeyEditorial Manager: Pete GaughanProduction Manager: Tim TateVice President and Executive Group Publisher: Richard SwadleyVice President and Publisher: Neil EddeBook Designer: Happenstance Type-O-Rama Compositor: Craig W. Johnson, Happenstance Type-O-RamaProofreader: Nancy BellIndexer: Ted LauxProject Coordinator, Cover: Katherine CrockerCover Designer: Ryan SneedCover Image: © Wayne Johnson/iStockPhoto

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Dear Reader,

Thank you for choosing Cisco Networking Essentials. This book is part of a family of premium-quality Sybex books, all of which are written by outstanding authors who combine practical experience with a gift for teaching.

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To my dear wife, Heike, who has supported me through

all the late nights working and missed weekends and who

has endured my ill temper throughout this process.

She is living proof there are angels among us.

Ack nowl edgments

I want to thank the entire editing and production staff that has helped to make this book as good as it can possibly be. That includes Kelly Talbot, my development editor, who gave me great advice beyond simply grammar and style. I took full advantage of all his years of experience as an editor. He was the conductor of this orchestra and ensured that everything was where it was sup-posed to be, when it was supposed to be.

I also would like to thank the technical editor, Leslie Herron, who saved me from myself a number of times. It is so comforting to know that someone with deep technical knowledge is looking over your shoulder. That also goes for Eric Charbonneau, who caught things that all of us missed, and the other members of the team, Pete Gaughan, Connor O’Brien, and Jenni Housh.

A special thanks goes to Jeff Kellum for recommending me for this book and to Agatha Kim, the acquisition editor, for selecting me for this book and helping to guide me through the entire process.

About the Author

Troy McMillan is a trainer and writer from Atlanta, Georgia. He began his IT career with IBM in 1999 supporting point-of-sale systems. After achieving his MCSE, he became a network administrator in the Atlanta office of a global manufacturer of electric motors. In 2000, he took his first job as a trainer, teaching MCSE classes to career changers at a local IT school in Atlanta.

In 2001, Troy started delivering corporate training for New Horizons in Atlanta. His concentration was in Microsoft, CompTIA, and Cisco classes. In 2002, Troy started his own training company while continuing with New Horizons on a contract basis and also teaching at various colleges and technical schools in the Atlanta area.

In 2003, Troy began traveling the United States and Canada, teaching Cisco, wireless (CWNA program), and Microsoft classes for training organizations such as Global Knowledge, New Horizons, PPI, and Knowlogy.

In 2005, Troy accepted a position with Kaplan IT Certification Preparation, creating practice tests and study guides for the Self-Test and Transcender brands. His work includes Microsoft, but he is the principal Cisco writer.

Troy’s first book, Change Your Career: Computer Network Security as Your New Profession, was released in 2007. This guide provides resources and helpful hints for career changers considering this field.

Troy began contributing to and providing technical edits for Sybex books in 2009. He contributed to Todd Lammle’s CCNA Wireless Study Guide: IUWNE Exam 640-721 and CompTIA Network+ Study Guide: Exam: N10-005, pro-vided technical edits and contributions to Todd’s CCNA Cisco Certified Network Associate Review Guide: Exam 640-802, and was technical editor for Darril Gibson’s Windows 7 Desktop Support and Administration: Real World Skills for MCITP Certification and Beyond (Exams 70-685 and 70-686). He is currently providing technical editing on Toby Skandier’s Network Administrator Street Smarts: A Real World Guide to CompTIA Network+ Skills.

In 2010, Troy coauthored VCP VMware Certified Professional on vSphere 4 Review Guide with Brian Perry, Chris Huss, and Jeantet Fields. He also created and edited textbooks for Penn Foster on Apple computers, basic troubleshoot-ing, and mobile devices. Troy created classroom instruction materials for many of the Sybex titles already listed as well as for MCTS: Windows Server 2008 R2 Complete Study Guide (Exams 70-640, 70-642 and 70-643) by William Panek.

Prior to his career in IT, Troy was a professional musician. From 1968 to 1986, he recorded and performed with many of his own bands and as a backup musi-cian for acts including Vassar Clements and Delbert McClinton. He worked for a number of years as a session musician and songwriter in Nashville as well. In 1983, he returned to school, earning a BBA in management from Georgia State University in 1986. He operated his own businesses after graduation as well as working several years in retail management. He began a self-study in IT in the 1990s, leading to his first IT job at IBM.

Troy lives with his wife, Heike, and a house full of dogs, cats, birds, and fish in Atlanta, Georgia. He enjoys running, music, and sports of all kinds, especially NASCAR.

contents At A gl Ance

Introduction xxi

CHAP TER 1 Networks 1

CHAP TER 2 The OSI Model 19

CHAP TER 3 TCP/IP 37

CHAP TER 4 Protocols 63

CHAP TER 5 Physical and Logical Topologies 89

CHAP TER 6 Numbering Systems 105

CHAP TER 7 Classful IP Addressing 125

CHAP TER 8 Classless IP Addressing 147

CHAP TER 9 Media 169

CHAP TER 10 Network Devices 193

CHAP TER 11 LAN Operations 215

CHAP TER 12 Managing the Cisco IOS 243

CHAP TER 13 Configuring Routers 271

CHAP TER 14 Configuring Switches 299

CHAP TER 15 Configuring Static Routing 317

CHAP TER 16 Configuring Dynamic Routing 331

APPENDIX Answers to Review Questions 349

Index 359

contents

Introduction xxi

chApter 1 Networks 1

Describing Network Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1Defining the Benefits of Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Identifying the Requirements for a Network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Classifying Networks by Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Understanding LANs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Understanding WANs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Defining Network Architectures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11Understanding Peer-to-Peer Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11Understanding Client-Server Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

The Essentials and Beyond. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

chApter 2 The OSI Model 19

Using Reference Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19Understanding the Benefits of Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Exploring Reference Model Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Introducing the Layers of the OSI Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22Understanding the Application Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23Understanding the Presentation Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23Understanding the Session Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Understanding the Transport Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26Understanding the Network Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29Understanding the Data-Link Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30Understanding the Physical Layer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Describing the OSI Encapsulation Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32Identifying the Process on the Source Device . . . . . . . . . . . . . . . . . . . . . . . . . . . 33Identifying the Process on the Destination Device . . . . . . . . . . . . . . . . . . . . . . . 34


C o n t e n t sx i v

chApter 3 TCP/IP 37

Understanding the TCP/IP Model. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38Exploring the Four Layers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39Comparing the OSI and TCP/IP Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

Describing the TCP/IP Encapsulation Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44Understanding Data and PDUs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44Describing the Contents of Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45Describing the Contents of Segments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45Describing the Contents of Packets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46Describing the Contents of Frames. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46Understanding the Conversion to Bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

Describing the Functions at the Transport Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . 48Understanding TCP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49Understanding UDP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Describing the Functions at the Internet Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52Defining Logical Addressing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52Performing Routing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53Accomplishing Packet Forwarding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

Describing the Functions of ARP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53Illustrating the ARP Broadcast . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54Describing the Logic of MAC-to-IP-Address Conversion . . . . . . . . . . . . . . . . . . . 56


chApter 4 Protocols 63

Understanding the Function of Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63Defining Routed Protocols. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64Defining Routing Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

Exploring Application Layer Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65Describing FTP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65Describing TFTP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67Describing SMTP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67Describing DNS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69Describing SNMP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

Exploring Transport Layer Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72Reviewing TCP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72Reviewing UDP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

C o n t e n t s x v

Exploring Internet Layer Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77Describing IP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77Describing ARP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79Describing ICMP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80Describing IGMP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

Exploring Network Access Layer Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83Defining Network Access Layer Protocols on the LAN . . . . . . . . . . . . . . . . . . . . 84Defining Network Access Layer Protocols on the WAN . . . . . . . . . . . . . . . . . . . . 85


chApter 5 Physical and Logical Topologies 89

Designing the Physical Topology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89Implementing a Bus Topology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90Implementing a Ring Topology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91Implementing a Star Topology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92Implementing a Mesh Topology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94Implementing a Hybrid Topology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95Implementing a Point-to-Point Topology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96Implementing a Point-to-Multipoint Topology. . . . . . . . . . . . . . . . . . . . . . . . . . . 98

Designing the Logical Topology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99Understanding the Token Ring Topology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99Understanding the FDDI Ring Topology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100Understanding the Star Topology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

The Essentials and Beyond. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

chApter 6 Numbering Systems 105

Exploring Binary Numbering. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105Understanding the Base-2 Numbering System. . . . . . . . . . . . . . . . . . . . . . . . . . 106Understanding the Relationship between Binary and Computers. . . . . . . . . . . 108

Exploring Hexadecimal Numbering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110Understanding the Base-16 Numbering System. . . . . . . . . . . . . . . . . . . . . . . . . 110Identifying MAC Addresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113

Applying Conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114Decimal-to-Binary Conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114Hex-to-Decimal Conversion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .117Binary-to-Hex Conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119


C o n t e n t sx v i

chApter 7 Classful IP Addressing 125

Describing the Function of IP Addresses. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126Segmentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127

Identifying IP Address Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128Defining IP Address Classes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129Identifying Network and Host Addresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130Describing Private IP Addresses and NAT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134

Utilizing Diagnostic Tools. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135Executing the ipconfig Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137Executing the ping Command. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137Executing the arp Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138Executing the traceroute Command. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

Understanding DHCP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139Cisco DHCP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141

Introducing IPv6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142IPv6 Address Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142IPv6 Address Types. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143Special IPv6 Addresses. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144

Essentials and Beyond . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144

chApter 8 C lassless IP Addressing 147

Understanding the Limitations of Classful Networking . . . . . . . . . . . . . . . . . . . . . 147Exhaustion of the Class B Network Address Space. . . . . . . . . . . . . . . . . . . . . . . 148Unmanageable Routing Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148Exhaustion of the 32-Bit IPv4 Address Space. . . . . . . . . . . . . . . . . . . . . . . . . . . 149

Understanding the Benefits of Subnetting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149Identifying Sources of Network Congestion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150Deploying Subnetting as a Segmentation Tool. . . . . . . . . . . . . . . . . . . . . . . . . . 151

Describing the Components of CIDR. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152Introducing Classless Subnetting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152Understanding VLSM. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161Summarization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166


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chApter 9 Media 169

Selecting the Proper Media Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169Bandwidth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170Security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170Convenience . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .174Cost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .174

Understanding Cabling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175Describing Cable Behavior and Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . 175Describing Physical Implementations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .176Choosing the Correct Wiring Standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180

Describing Wireless Standards. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184Identifying Standards Bodies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185Understanding 802.11 Amendments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185Understanding Wireless LAN Components and Terminology . . . . . . . . . . . . . . 187Describing CSMA/CA Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189


chApter 10 Network Devices 193

Describing Device Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193Understanding Repeaters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194Understanding Hubs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194Understanding Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195Understanding Switches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197Understanding Routers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201Understanding Wireless Access Points and Wireless Routers . . . . . . . . . . . . . . 205

Understanding Device Placement Principles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207Defining Broadcast Domains. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207Defining Collision Domains. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208Understanding the Cisco Three-Layer Model . . . . . . . . . . . . . . . . . . . . . . . . . . . 211


chApter 11 LAN Operations 215

Understanding the Routing Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215Describing Routing Tables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216Understanding Population Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219Understanding Administrative Distance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221Using Routing Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223

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Describing the Switching Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232Reviewing MAC and IP Addresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233Reviewing Contention Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234Describing MAC Address Tables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235Understanding Frame Forwarding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236

Describing End-to-End Communications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237Understanding the Local LAN Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237Understanding the Remote Communication Process . . . . . . . . . . . . . . . . . . . . 238


chApter 12 Managing the Cisco IOS 243

Describing Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243Defining the Contents of RAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244Defining the Contents of NVRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245Defining the Contents of Flash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245Defining the Contents of ROM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246

Describing IOS Navigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248Connecting to the Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248Accessing User, Privileged, and Global Configuration Modes . . . . . . . . . . . . . . 252

Understanding and Managing the Boot Process . . . . . . . . . . . . . . . . . . . . . . . . . . . 256Understanding the Boot Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257Managing the IOS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260Understanding Configuration Files. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261Managing the Configuration Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263


chApter 13 Conf iguring Routers 271

Cabling the Router . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271Cabling Router to Router. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274Cabling Router to Switch. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276Cabling PC to Router . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277Cabling Router to CSU/DSU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 279

Creating a Console Session . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280Connecting with the Console Cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280Connecting through Telnet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281Handling Initial Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 282

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Configuring Passwords. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 282Interpreting Prompts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 282Configuring Privileged (Enable) Passwords . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283Configuring Enable Secret Passwords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284Configuring Line Passwords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284

Configuring Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 286Accessing Interface Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 286Assigning an IP Address. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287Enabling the Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288Verifying the Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288Enabling DHCP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290Configuring WAN Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292

Saving Configuration Changes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294The Essentials and Beyond. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295

chApter 14 Conf iguring Switches 299

Cabling the Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299Cabling Switch to Switch. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300Cabling Router to Switch. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301Cabling Hosts to Switch. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302

Creating a Session with the Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302Creating a Session with the Console Cable. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303Creating a Session through Telnet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304

Configuring Passwords. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305Configuring Privileged (Enable) Passwords . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305Configuring Enable Secret Passwords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306Configuring Line Passwords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306

Configuring Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306Accessing Switchports and Using Switchport Mode. . . . . . . . . . . . . . . . . . . . . . 306Enabling the Port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307Verifying the Port. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307

Understanding Advanced Switch Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308Understanding VLANs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308Understanding Trunk Ports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310Describing STP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311


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chApter 15 Conf iguring Stat ic Routing 317

Populating the Routing Table. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 318Using the ip route Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 318Verifying the Route Table. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320

Configuring Inter-VLAN Routing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321Creating a Trunk Link with Encapsulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322Creating and Configuring Subinterfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323


chApter 16 Conf iguring Dynamic Routing 331

Understanding Routing Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331Exploring RIP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333Exploring EIGRP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335Exploring OSPF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336

Configuring Routing Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336Enabling a Routing Protocol and Accessing Router Mode. . . . . . . . . . . . . . . . . 337Defining the Interfaces on Which the Protocol Is Operational . . . . . . . . . . . . . 338Verifying the Routing Table. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340

Appendix Answers to Review Questions 349

Index 359

introduc t ionThis book is designed to fill a gap that has existed for some time in techni-cal books and instructional materials covering networking in general and Cisco technology in particular. As a trainer, I have struggled to find materials that strike a middle ground between basic networking texts and books that jump immediately into certification-level topics that many readers and students are not prepared to digest.

There will always be a market for books designed to present and review certification-level topics to those who are already familiar with the knowledge required to understand those topics. In today’s economic times, however, there is a whole new breed of students who are either taking classes or operating in a self-study capacity but do not have this prerequisite knowledge and may not even realize this as they attempt to tackle certification-level classes and books.

I have seen these students in my classes over the years. They are no less intel-ligent or motivated than the students who have more background and experi-ence. But at the pace at which these books and classes must move to cover all the material, they soon find themselves struggling. Some even give up entirely.

This book covers all of the basic knowledge required for you to really under-stand routing and switching. It provides the required amount of time for you to digest the fundamentals before moving on to actually setting up and configur-ing the routers and switches and seeing them operate. It does not attempt to cover every bell and whistle that these devices offer, nor does it cover every topic that is on a Cisco CCENT exam. What it does do is provide all of the basic net-work knowledge from a Cisco perspective.

The student who reads this book and works through these exercises or the student who takes a class using this book as its text will come away ready in every way to tackle books and classes targeted for exam prep for the CCNA. That is the goal of this book and was our guiding principle throughout its creation.

Who Should Read This BookThis book is designed for anyone wishing to gain a basic understanding of how networks operate and how Cisco devices in particular fulfill their roles in the process. This includes the following:

�� Those who have been away from the IT industry for some time and are reentering the field

�� Career changers with no previous experience

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�� Students who have struggled with certification-level prep materials

�� Students who have had success with certification-level prep materials but came away from the experience with a shallow understanding of the core foundational knowledge

What’s InsideHere is a glance at what’s in each chapter:

Chapter 1, “Networks,” describes network components, classifies LANs and WANs by function, and compares and contrasts peer-to-peer and client-server networks.

Chapter 2, “The OSI Model,” explains the purpose of reference models, intro-duces the layers of the OSI model, and describes how the layers relate to the encapsulation process.

Chapter 3, “TCP/IP,” explains the TCP/IP reference model, compares it to the OSI model, and describes the function of the four layers of the model.

Chapter 4, “Protocols,” describes the function of protocols in networking and surveys various protocols that operate at each layer of the TCP/IP model.

Chapter 5, “Physical and Logical Topologies,” defines the meaning of a topol-ogy in networking and describes the main physical and logical topologies.

Chapter 6, “Numbering Systems,” explains the main numbering systems of importance in networking, the binary and hexadecimal systems, and how they are converted to and from the decimal system.

Chapter 7, “Classful IP Addressing,” explains the basics of IP addressing, identi-fies the types of IP addresses, introduces network troubleshooting tools, and describes the use of DHCP to automate the IP configuration process.

Chapter 8, “Classless IP Addressing,” points out the shortcomings of classful IP addressing, explains the benefits of classless subnetting, and introduces the components of CIDR.

Chapter 9, “Media,” begins with a brief description of media types, explains cable behaviors and characteristics, and ends with a survey of the types of cables and their proper use.

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Chapter 10, “Network Devices,” describes the functions of the various devices found in a network and explains design principles guiding their placement.

Chapter 11, “LAN Operations,” explains both the routing and the switching process and describes how they fit together in end-to-end communication.

Chapter 12, “Managing the Cisco IOS,” introduces the components of the Cisco operating system, describes the boot process of a router or switch, and describes how to navigate the command-line interface.

Chapter 13, “Configuring Routers,” explains how to get a router operational, including cabling the router, logging into the IOS, securing the router, and con-figuring its interfaces.

Chapter 14, “Configuring Switches,” explains how to get a switch operational, including cabling the switch, logging into the IOS, securing the switch, config-uring its switchports, and creating and managing VLANs.

Chapter 15, “Configuring Static Routing,” explains how routes are configured and verified at the CLI and how to configure inter-VLAN routing.

Chapter 16, “Configuring Dynamic Routing,” introduces how dynamic routing functions, explains the types of routing protocols, and describes how to config-ure an example of each.

NOTEEach chapter contains Additional Exercises and Review Questions. The answers to the Review Questions can be found in the book’s Appendix. Please visit the book’s companion website (www.sybex.com/go/ ciscoessentials) to compare your answers to the Additional Exercises with the author’s answers.

How to Contact the AuthorI welcome feedback from you about this book or about books you’d like to see from me in the future. You can reach me by writing to [email protected] or [email protected].

http://www.sybex.com/go/ciscoessentials

http://www.sybex.com/go/ciscoessentials



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Sybex strives to keep you supplied with the latest tools and information you need for your work. Please check their website at www.sybex.com, where we’ll post additional content and updates that supplement this book should the need arise. Enter Cisco Essentials in the Search box (or type the book’s ISBN—918-1-118-09759-5), and click Go to get to the book’s update page.

http://www.sybex.com

CHAPTER 1

NetworksComputer networks are everywhere. It’s impossible to escape them in the modern world in which we live and work. We use them at work, at home, and even in between, in places like our cars, the park, and the coffee shop. We have come to take them for granted in the same way we treat electricity and hot water.

But a lot is going on behind the scenes when we use these networks. Cisco routers and switches play a critical role in networks’ successful operation.

This opening chapter lays the foundation required to understand all the details that make networks function. Specifically, this chapter covers the fol-lowing topics:

�� Describing network components

�� Classifying networks by function

�� Defining network architectures

Describing Network ComponentsTo understand how networks work, it helps to have an appreciation of why they exist in the first place. As incredible as it may seem now, for a number of years, when computers first came into use, very few computers were net-worked. They operated as little islands of information with no connection to one another. Data had to be transferred between computers by copying it to a floppy disk, physically taking that floppy disk to the other computer, and copying the data to the destination machine. This process is now sometimes jokingly referred to as the sneakernet.

Modern networks can include many components. Some of the most basic components are computers, routers, and switches. Figure 1.1 shows some Cisco routers and switches. Routers are used in a network to transfer infor-mation between computers that are not on the same network. Routers are

C h a p t e r 1 • N e t w o r k s2

capable of doing this by maintaining a table of all networks and the routes (direc-tions) used to locate those networks. Switches come in two varieties. Layer 2 switches simply connect computers or devices that are in the same network. Layer 3 switches can do that but are capable of acting as routers as well. Two models of routers are depicted in Figure 1.1, with a switch in the middle of the stack. Routers and switches are covered in depth in Chapter 10, “Network Devices.”

F I G U R E 1 . 1 Cisco routers and switches

In this section, the benefits of networking are covered as well as the compo-nents required to constitute a network.

Defining the Benefits of NetworksThere are many benefits to networks, one of which was touched on in the introduction to this section: using a network makes sharing resources possible (without putting on your sneakers and leaving your seat). When connected by networks, users can share files, folders, printers, music, movies, you name it!

D e s c r i b i n g N e t w o r k C o m p o n e n t s 3

If it can be put on a hard drive, it can be shared. Additional benefits are included in the following list:

Resource Sharing Resource sharing is less earthshaking at home, but in the workplace it was a key element that drove the adoption of PCs. Other computer types such as mainframe computers and dumb terminals were already in use, but were seen as specialized pieces of equipment to be used only by guys in lab coats and some other geeky types. There were other reasons for the PC revolution, but resource sharing helped to increase productivity. As an example, 10 coworkers could access a file on the network at the same time, which eliminated the time and effort spent burning, labeling, transporting, and storing 10 floppies.

Reduced Cost and Easier Installation of Software Another advantage for busi-ness that didn’t become apparent as quickly as resource sharing was a reduced cost of software. Many software products are sold to organizations on a network basis. For example, instead of buying 25 retail versions of word processing software, a single copy can be purchased for the network and then a number of seat licenses can be added to the bundle. The result is a significant savings to the company.

Taking that idea a step further, the network also makes it possible to place the installation files (from the CD containing the software) on a server and to then install the software over the network (as shown in Figure 1.2). This capability relieves IT staff from having to physically visit each machine with CD in hand to perform the installation. Moreover, the software could be installed on all five machines at once over the network by using those same files.

Distribution ServerTarget Computer

Target Computer

Target Computer Target Computer

Target Computer

InstallationFiles

F I G U R E 1 . 2 Network installation

O

The term resource is used extensively when discussing networking and simply refers to any-thing that a user on one computer may want to access on a different computer. Examples include files, folders, print-ers, and scanners.

C h a p t e r 1 • N e t w o r k s4

Improved Security All this peace, love, and sharing doesn’t mean that every-thing is available to everyone. Shared resources can be secured with restrictions on who can access them and what exact access each individual possesses. So you can share a file on your computer but share it with only two of your cowork-ers, and not all of them. Moreover, you could allow one coworker to only read the document while the other could be allowed to edit or even delete the document.

This type of control was difficult when files were shared on floppies. After the floppy left your hand, it was out of your control. Computer networks can enforce security controls among the computers and users.

Improved Communications It’s hard to even imagine today’s workplace without email, instant messaging, video chatting, and conferencing, but 25 years ago, these tools did not exist. In today’s world, almost no communication can wait for regular postal mail (this service that we once depended on is now often called snail mail). Even more impressive is that distance is no obstacle. You can chat online with someone in India or China as easily as with a fellow worker sitting in the next cubical!

Now think of all the paper that is being saved that used to be consumed by com-panies sending regular mail to one another. The problem was multiplied by the need to keep multiple copies of the documents sent through the regular mail. Email systems can be configured to maintain a copy of every email sent, and documents that used to exist in multiple physical copies now reside as a single digital copy on a server (and probably also on a backup tape).

Meetings that used to require plane trips and hotel stays can now be held online with all participants able to see one another, share documents, view slides or documents from the presenter, and even hold votes and surveys. The only con-sideration is time zones!

More Workplace Flexibility Users are no longer physically tied to the same computer. If resources are stored on servers, as they are in most organizations, a computer problem no longer renders a user unable to work. In a domain-based network (more on that later in this chapter in the section “Understanding Client-Server Networks”), the user can move to any other computer that is a member of the domain, access his files on the server, and continue to work while his computer is repaired or replaced.

Building on this idea, workers are increasingly telecommuting as they can use the Internet to connect to the work network and operate as if physically present in the office.

Telecommuting means working from another physical location, usually from home. It saves gas, time, and in many cases results in more productivity on the part of the worker.

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CISCO NETWORKING · MCITP Certification and Beyond (Exams 70-685 and 70-686). He is currently...

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