CCNA for Dummies

305 Pages·2000·1.061 MB·English

by  Ron Gilster

Table of Contents
CCNA for Dummies...........................................................................................................................................1
Overview.................................................................................................................................................1
About the Authors...................................................................................................................................2
Dedication...............................................................................................................................................3
Authors(cid:25) Acknowledgments..................................................................................................................3
Publisher(cid:25)s Acknowledgments..............................................................................................................3
Introduction........................................................................................................................................................5
Overview.................................................................................................................................................5
Why Use This Book?..............................................................................................................................5
Using This Book.....................................................................................................................................6
Part I: The Basics.............................................................................................................................6
Part II: The OSI Reference Model...................................................................................................6
Part III: Routers................................................................................................................................6
Part IV: Network Protocols..............................................................................................................6
Part V: LANs and WANs.................................................................................................................6
Part VI: The Part of Tens.................................................................................................................6
Part VII: Appendixes........................................................................................................................7
What(cid:25)s on the CD............................................................................................................................7
Studying Chapters...................................................................................................................................7
First page..........................................................................................................................................7
Quick Assessment questions............................................................................................................7
Study subjects...................................................................................................................................7
Prep Tests.........................................................................................................................................9
Icons Used in This Book.........................................................................................................................9
Feedback.................................................................................................................................................9
Part I: The Basics.............................................................................................................................................10
Chapter List............................................................................................................................................10
In this part&....................................................................................................................................10
Chapter 1: The CCNA Examination..............................................................................................................11
In This Chapter.....................................................................................................................................11
A Little Background about the CCNA Exam.......................................................................................11
What(cid:25)s included in CCNA certification?......................................................................................11
Who should get CCNA certification?............................................................................................12
Is CCNA related to other certifications?........................................................................................12
The Cisco Networking Academy program.....................................................................................13
Why Get CCNA Certification?.............................................................................................................13
What the CCNA Exam Covers.............................................................................................................13
OSI Reference Model.....................................................................................................................16
WAN protocols...............................................................................................................................16
Cisco IOS commands.....................................................................................................................16
Network protocols..........................................................................................................................16
Routing...........................................................................................................................................16
Network security............................................................................................................................16
LAN switching...............................................................................................................................16
Cisco career certification and survey.............................................................................................17
Taking (And Passing) the Exam...........................................................................................................17
Preparing for the Exam.........................................................................................................................17
Signing up to Take the Exam................................................................................................................18
How Much Does It Cost?......................................................................................................................18
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Table of Contents
Chapter 1: The CCNA Examination
World Wide Web Sites to Help You.....................................................................................................18
Where to Go from Here........................................................................................................................19
A Little Luck Never Hurts....................................................................................................................19
Chapter 2: The Language of the CCNA Exam.............................................................................................20
In This Chapter.....................................................................................................................................20
Laying Out the Network Topology.......................................................................................................20
Please accept our topologies...........................................................................................................20
Mixed topologies............................................................................................................................21
Applying LAN Technologies................................................................................................................22
Ethernet networks...........................................................................................................................22
Token Ring networks.....................................................................................................................22
FDDI: The double−ring network....................................................................................................22
Defining LANs, MANs, and WANs.....................................................................................................22
Designing Networks: An Overview......................................................................................................23
Subnet Mask Review............................................................................................................................24
Part II: The OSI Reference Model.................................................................................................................26
Chapter List............................................................................................................................................26
In this part&..........................................................................................................................................26
Chapter 3: Routing Through the OSI Model................................................................................................27
Exam Objectives...................................................................................................................................27
Quick Assessment.................................................................................................................................27
Answers.................................................................................................................................................28
The OSI: A Model of Efficiency..........................................................................................................28
Reasons why a layered−model is used...........................................................................................28
The layers of the OSI model...........................................................................................................29
Packaging the data..........................................................................................................................30
Down one side and up the other.....................................................................................................31
Getting Physical....................................................................................................................................32
Electrically speaking......................................................................................................................32
Getting to know the wire................................................................................................................32
Choosing the network cable...........................................................................................................32
Working in the Wiring Closet...............................................................................................................34
Wiring standards.............................................................................................................................34
Cross−connecting the backbone.....................................................................................................35
Physical Layer Hardware......................................................................................................................36
Could you repeat that?....................................................................................................................36
Just a hub of activity.......................................................................................................................36
Prep Test...............................................................................................................................................37
Answers.................................................................................................................................................39
Chapter 4: The Data Link Layer....................................................................................................................40
Exam Objectives...................................................................................................................................40
Quick Assessment.................................................................................................................................40
Answers.................................................................................................................................................41
Working on the Data Link Layer..........................................................................................................41
Listing the functions of Layer 2.....................................................................................................41
Stacking up the IEEE 802 standards..............................................................................................42
Ethernet and the mighty 802.3.......................................................................................................43
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Table of Contents
Chapter 4: The Data Link Layer
The sublayers of the Data Link layer.............................................................................................43
Controlling access to the network..................................................................................................45
Segmenting a Network for Fun and Profit............................................................................................46
Reaping the benefits of segmentation............................................................................................47
Bridging the difference...................................................................................................................47
Encapsulating Data...............................................................................................................................49
Prep Test...............................................................................................................................................50
Answers.................................................................................................................................................52
Chapter 5: The Network Layer......................................................................................................................54
Exam Objectives...................................................................................................................................54
Quick Assessment.................................................................................................................................54
Answers.................................................................................................................................................54
Reviewing Routing Foundations..........................................................................................................55
Addressing it logically....................................................................................................................55
Moving a packet across the internetwork.......................................................................................56
Comparing routed and routing protocols........................................................................................56
Choosing static or dynamic routes.................................................................................................57
Routing, or is that rooting?.............................................................................................................57
Layer 3 devices and protocols........................................................................................................57
Routing IPX and other NetWare Stuff..................................................................................................58
Broadcasting the SAP.....................................................................................................................58
Can I get your IPX address?...........................................................................................................59
Do you have an IPX socket wrench?..............................................................................................59
Configuring the router for IPX.......................................................................................................59
Enabling IPX globally....................................................................................................................60
Interfacing locally...........................................................................................................................60
Prep Test...............................................................................................................................................61
Answers.................................................................................................................................................62
Chapter 6: The Transport Layer....................................................................................................................64
Exam Objectives...................................................................................................................................64
Quick Assessment.................................................................................................................................64
Answers.................................................................................................................................................65
Transporting Data Over the Network...................................................................................................65
Supporting the transport services...................................................................................................66
Transporting protocols...................................................................................................................66
Getting Well Connected........................................................................................................................67
The benefits of being connection−oriented....................................................................................67
Using a connectionless protocol.....................................................................................................67
Making a positively reliable delivery.............................................................................................68
Making a Fast Recovery.......................................................................................................................68
Identifying an error recovery protocol...........................................................................................68
Checking for errors.........................................................................................................................69
It(cid:25)s 100 milliseconds, do you know where your data is?..............................................................69
Going with the Flow and Staying in Control........................................................................................70
Smoothing out the bumps...............................................................................................................70
Avoiding the congestion.................................................................................................................70
Flowing through the windows........................................................................................................70
Quenching the source.....................................................................................................................71
Prep Test...............................................................................................................................................71
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Table of Contents
Chapter 6: The Transport Layer
Answers.................................................................................................................................................73
Chapter 7: The Upper Layers.........................................................................................................................74
Exam Objectives...................................................................................................................................74
Quick Assessment.................................................................................................................................74
Answers.................................................................................................................................................75
Communicating on the Session Layer..................................................................................................75
Communicating a la mode..............................................................................................................75
Testing your session skills..............................................................................................................77
Presenting the Presentation Layer.........................................................................................................77
Applying the Application Layer...........................................................................................................78
A Quick Review of the OSI Model.......................................................................................................78
Prep Test...............................................................................................................................................79
Answers.................................................................................................................................................81
Part III: Routers..............................................................................................................................................83
Chapter List............................................................................................................................................83
In this part&....................................................................................................................................83
Chapter 8: Router Models...............................................................................................................................84
Exam Objectives...................................................................................................................................84
Quick Assessment.................................................................................................................................84
Answers.................................................................................................................................................85
A Layered Approach to Networks........................................................................................................85
Core layer routers...........................................................................................................................86
Distribution layer routers................................................................................................................86
Access layer routers........................................................................................................................86
Segmenting a Network with a Router...................................................................................................86
Why segment a network?...............................................................................................................87
Segmenting a LAN with a router...................................................................................................87
The specific benefits of segmenting with a router.........................................................................88
The Four Faces of Router Memory.......................................................................................................88
RAM/DRAM a ding dong..............................................................................................................89
Good old stable, non−volatile RAM..............................................................................................89
ROM is not RAM...........................................................................................................................89
Flashing the EPROM......................................................................................................................90
Discovering CDP..................................................................................................................................90
CDP protocol facts.........................................................................................................................90
How CDP works.............................................................................................................................90
Stuff to memorize about CDP........................................................................................................90
Prep Test...............................................................................................................................................91
Answers.................................................................................................................................................93
Chapter 9: Router Basics................................................................................................................................94
Exam Objectives...................................................................................................................................94
Quick Assessment.................................................................................................................................94
Answers.................................................................................................................................................95
Oh Phooey, There(cid:25)s No GUI...............................................................................................................95
Spelling and syntax: Getting it right...............................................................................................95
Accessing the router.......................................................................................................................96
Logging into the router...................................................................................................................96
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Table of Contents
Chapter 9: Router Basics
Working with the Exec command interpreter................................................................................97
Other command modes you may see on the test............................................................................97
Getting By with a Little Help...............................................................................................................99
What is a four−letter word beginning with an (cid:28)h?(cid:29) ......................................................................99
Show me everything and let me pick.............................................................................................99
Help for the terminally lazy..........................................................................................................100
Okay, show me the rest................................................................................................................100
Editing History....................................................................................................................................100
Life is good with enhanced editing..............................................................................................100
Changing history..........................................................................................................................101
Your Router Needs a Name................................................................................................................101
Let(cid:25)s Play Password...........................................................................................................................102
Don(cid:25)t be so sensitive...................................................................................................................102
Getting into configuration mode..................................................................................................102
Changing the locks.......................................................................................................................102
Giving the Router an Identity.............................................................................................................104
Waving the Banner.............................................................................................................................104
Inserting descriptions where you need them................................................................................105
Prep Test.............................................................................................................................................105
Answers...............................................................................................................................................107
Chapter 10: Router Commands...................................................................................................................108
Exam Objectives.................................................................................................................................108
Quick Assessment...............................................................................................................................108
Answers...............................................................................................................................................109
Setting up and Configuring a Router..................................................................................................109
Watch out, it(cid:25)s a setup!................................................................................................................109
What(cid:25)s the password?..................................................................................................................110
Setting up the interface.................................................................................................................110
If You Start It up, It Never Stops........................................................................................................111
POST it up....................................................................................................................................111
Are you registered?......................................................................................................................111
Changing your boots....................................................................................................................112
It(cid:25)s not a trivial matter.................................................................................................................112
Backing up the flash.....................................................................................................................112
Now that it(cid:25)s started, back it up!.................................................................................................113
A command performance.............................................................................................................114
The Manual Approach to Configuration.............................................................................................115
Prep Test.............................................................................................................................................115
Answers...............................................................................................................................................117
Chapter 11: RIP, IGRP, IPX, and Convergence.........................................................................................119
Exam Objectives.................................................................................................................................119
Quick Assessment...............................................................................................................................119
Answers...............................................................................................................................................120
Routed Versus Routing Protocols.......................................................................................................120
Inside versus outside....................................................................................................................120
A routing we will go.....................................................................................................................121
Routing types you need to know for the exam.............................................................................121
Plotting the Best Course.....................................................................................................................122
Moving to the algorithm...............................................................................................................122
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Table of Contents
Chapter 11: RIP, IGRP, IPX, and Convergence
Routing Algorithms............................................................................................................................123
Going the distance........................................................................................................................123
The state of the network...............................................................................................................126
Classful Routing.................................................................................................................................126
Let (cid:25)er RIP...................................................................................................................................126
IGRP routing................................................................................................................................128
Routing for the Novell riche.........................................................................................................128
Prep Test.............................................................................................................................................131
Answers...............................................................................................................................................133
Part IV: Network Protocols..........................................................................................................................134
Chapter List..........................................................................................................................................134
In this part&..................................................................................................................................134
Chapter 12: Network Addressing.................................................................................................................135
Exam Objectives.................................................................................................................................135
Quick Assessment...............................................................................................................................135
Answers...............................................................................................................................................136
Getting the Address Right...................................................................................................................136
MAC addresses.............................................................................................................................136
Working with IP addresses...........................................................................................................138
IP address classes.........................................................................................................................139
The Curse of the Subnet Mask............................................................................................................141
Boolean nightmares......................................................................................................................142
Classy masks................................................................................................................................142
It(cid:25)s only a trial separation............................................................................................................143
Routing IP Addresses..........................................................................................................................143
Configuring an IP address............................................................................................................143
Verifying an IP address................................................................................................................144
Prep Test.............................................................................................................................................146
Answers...............................................................................................................................................148
Chapter 13: Subnetting.................................................................................................................................149
Exam Objectives.................................................................................................................................149
Quick Assessment...............................................................................................................................149
Answers...............................................................................................................................................150
Subnetting...........................................................................................................................................150
Subnetting networks ID................................................................................................................150
Subnetting, subnet, and subnet mask............................................................................................151
Subnetting for fun and profit........................................................................................................151
Borrowing bits to grow a subnet..................................................................................................152
Knowing how to calculate subnets...............................................................................................154
A short broadcast..........................................................................................................................157
A Little Bit of Practice........................................................................................................................157
Calculating subnets, hosts, and broadcast addresses....................................................................157
Another subnet problem, but just a little harder...........................................................................158
A Class B subnet problem............................................................................................................159
Subnet planning problem..............................................................................................................159
Prep Test.............................................................................................................................................160
Answers...............................................................................................................................................162
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Table of Contents
Chapter 14: TCP/IP.......................................................................................................................................163
Exam Objectives.................................................................................................................................163
Quick Assessment...............................................................................................................................163
Answers...............................................................................................................................................164
The TCP/IP Suite................................................................................................................................164
The TCP/IP protocols...................................................................................................................164
TCP/IP protocol stack..................................................................................................................165
Application layer protocols..........................................................................................................166
Transport Layer Protocols...................................................................................................................166
Transmission Control Protocol (TCP)..........................................................................................166
Getting to know the well−known ports........................................................................................169
Formatting the TCP segment........................................................................................................170
User Datagram Protocol (UDP)...................................................................................................171
The UDP datagram.......................................................................................................................171
Network Layer Protocols....................................................................................................................172
Internet Protocol (IP)....................................................................................................................172
Internet Control Message Protocol (ICMP).................................................................................174
Address Resolution Protocol (ARP).............................................................................................174
Reverse ARP (RARP)..................................................................................................................174
Data Encapsulation.............................................................................................................................175
Prep Test.............................................................................................................................................175
Answers...............................................................................................................................................177
Chapter 15: Security......................................................................................................................................179
Exam Objectives.................................................................................................................................179
Quick Assessment...............................................................................................................................179
Answers...............................................................................................................................................180
Configuring IP Access Lists...............................................................................................................180
IP access lists................................................................................................................................180
Filtering port traffic......................................................................................................................184
Named access lists........................................................................................................................184
Removing an access list...............................................................................................................184
Verifying the access list...............................................................................................................185
Novell IPX Access Lists.....................................................................................................................185
Standard IPX access lists..............................................................................................................186
IPX extended access lists.............................................................................................................186
SAP filters....................................................................................................................................187
Prep Test.............................................................................................................................................187
Answers...............................................................................................................................................189
Part V: LANs and WANs..............................................................................................................................191
Chapter List..........................................................................................................................................191
In this part&..................................................................................................................................191
Chapter 16: LAN Switching..........................................................................................................................192
Exam Objectives.................................................................................................................................192
Quick Assessment...............................................................................................................................192
Answers...............................................................................................................................................193
Switching Around the Network..........................................................................................................193
Talking about switches.................................................................................................................193
Switches and LANs......................................................................................................................194
Segmenting a LAN.............................................................................................................................194
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Table of Contents
Chapter 16: LAN Switching
Segmentation: A quick overview.................................................................................................195
Segmenting a LAN with a bridge.................................................................................................195
Segmenting the LAN with a router..............................................................................................196
Segmenting a LAN with a switch.................................................................................................196
Applying Three Methods to Switching Success.................................................................................197
Virtually Segmenting the LAN...........................................................................................................197
Reaping the benefits of a VLAN..................................................................................................197
Configuring the VLAN one way or another.................................................................................199
Trunking together VLANs...........................................................................................................199
Prep Test.............................................................................................................................................200
Answers...............................................................................................................................................202
Chapter 17: Connecting with WAN Protocols............................................................................................203
Exam Objectives.................................................................................................................................203
Quick Assessment...............................................................................................................................203
Answers...............................................................................................................................................204
Differentiating WAN Services............................................................................................................204
Connecting with the mysterious X.25..........................................................................................204
The framer in the DLCI................................................................................................................207
ISDN and the LAPD.....................................................................................................................208
High−level communications........................................................................................................208
Getting point−to−point.................................................................................................................208
Recognizing Frame Relay...................................................................................................................209
Framing the Frame Relay frame...................................................................................................210
Flagging congestion in Frame Relay............................................................................................210
Throwing out everything over the limit.......................................................................................211
Configuring Frame Relay switching on a router..........................................................................212
So what(cid:25)s the LMI?.....................................................................................................................212
Mapping the IP to the DLCI.........................................................................................................212
Singing the subinterface homesick blues.....................................................................................213
Configuring Frame Relay.............................................................................................................213
Monitoring Frame Relay..............................................................................................................214
PPP WAN Encapsulation....................................................................................................................214
Putting ISDN to Use...........................................................................................................................215
Defining some ISDN basics.........................................................................................................215
Identifying the ISDN twins: PRI and BRI....................................................................................216
Working with ISDN BRI on a Cisco Router......................................................................................217
Prep Test.............................................................................................................................................217
Answers...............................................................................................................................................219
Part VI: The Part of Tens.............................................................................................................................221
Chapter List..........................................................................................................................................221
In this part&..................................................................................................................................221
Chapter 18: Ten Really Great Sites for Study Aids....................................................................................222
In This Chapter...................................................................................................................................222
Cisco Systems, Inc..............................................................................................................................222
BeachFront Quizzer............................................................................................................................222
Boson Software, Inc............................................................................................................................222
CramSession.com...............................................................................................................................223
MeasureUp, Inc...................................................................................................................................223
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Table of Contents
Chapter 18: Ten Really Great Sites for Study Aids
MentorLabs.........................................................................................................................................223
SelfTest Software................................................................................................................................223
Welcome.to/CCNA.............................................................................................................................223
The TechWeb Encyclopedia...............................................................................................................223
Whatis.com.........................................................................................................................................223
amazon.com, barnesandnoble.com, borders.com, and fatbrain.com..................................................224
And a Few More Good Sites to Visit..................................................................................................224
Chapter 19: Ten Things to Do on Your Test Day.......................................................................................225
In This Chapter...................................................................................................................................225
Get Me to the Test on Time................................................................................................................225
Arrive Early........................................................................................................................................225
Review Your Notes One Last Time....................................................................................................226
Check In on Time................................................................................................................................226
Do a Brain Dump, But Do It on the Plastic........................................................................................226
Do the Tutorial!...................................................................................................................................226
Ready, Steady, Go...............................................................................................................................227
A New Wrinkle: There(cid:25)s No Going Back!........................................................................................227
No Hootin(cid:25) and Hollerin(cid:25) Please......................................................................................................227
Part VII: Appendixes.....................................................................................................................................228
Chapter List..........................................................................................................................................228
In this part&..................................................................................................................................228
Appendix A: Sample Test..............................................................................................................................229
Overview.............................................................................................................................................229
The OSI Reference Model............................................................................................................229
WAN Protocols............................................................................................................................232
Cisco IOS Commands..................................................................................................................235
Network Protocols........................................................................................................................237
Routing.........................................................................................................................................238
Network Security..........................................................................................................................241
LAN Switching.............................................................................................................................242
Answers...............................................................................................................................................245
Appendix B: About the CD...........................................................................................................................251
Overview.............................................................................................................................................251
System Requirements.........................................................................................................................251
Using the CD with Microsoft Windows.............................................................................................251
What You(cid:25)ll Find on the CD..............................................................................................................252
Dummies test prep tools...............................................................................................................253
Commercial demos.......................................................................................................................253
If You(cid:25)ve Got Problems (Of the CD Kind).......................................................................................254
Appendix C: Glossary....................................................................................................................................256
Overview.............................................................................................................................................256
Index...................................................................................................................................................265
A...................................................................................................................................................265
Index...................................................................................................................................................266
B...................................................................................................................................................266
Index...................................................................................................................................................266
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