CCNP Self-Study CCNP BSCI Exam Certification Guide

Cisco Press
201 W 103rd Street
Indianapolis, IN 46290
Cisco Press

CCNP Self-Study

CCNP BSCI Exam
Certification Guide

Clare Gough

chpt_01.book Page i Thursday, January 9, 2003 4:32 PM

ii

CCNP BSCI Exam Certification Guide

Clare Gough
Copyright © 2003 Cisco Systems, Inc.
Published by:
Cisco Press
201 West 103rd Street
Indianapolis, IN 46290 USA
All rights reserved. No part of this book may be reproduced or transmitted in any form or by any means, electronic or
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Printed in the United States of America 1 2 3 4 5 6 7 8 9 0
First Printing January 2003
Library of Congress Cataloging-in-Publication Number: 20-02115641

ISBN: 1-58720-078-3

Warning and Disclaimer

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Publisher John Wait
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About the Author

Clare Gough

, CCIE No. 2893, has been a certified Cisco Systems instructor for the ICRC, ACRC, CIT, CLSC, and
CID courses. She holds a master's degree in education and a master’s degree in information systems. Over the last 15
years, she has developed and taught a variety of networking and internetworking courses throughout the world for
Digital Equipment Company and various Cisco training partners. She moved from England in 1991 and now lives in
San Francisco with her family.

About the Technical Reviewers

Jorge Aragon,

CCIE No. 5567, is a network engineer with Perot Systems Corporation (PSC) in Dallas, Texas. He
holds a bachelor of science degree in electrical engineering from the National Polytechnic Institute in Mexico, and
has a master of science degree in telecommunications from the University of Pittsburgh. He also holds an MCSE
certification and several Cisco specializations. Jorge is part of the PSC Global Infrastructure team, where he designs,
implements, and troubleshoots LAN and WAN networks for clients in multiple industries across the globe. He
enjoys spending time with his wife and children, reading, jogging, and practicing martial arts. Jorge can be reached
at

Steve Gifkins

is a CCIE and CCSI of four and five years, respectively. He is based in the United Kingdom, where he
runs his own independent Cisco-only consulting and training business. He is married with no children, and his hob-
bies include anything to do with outdoor life. Having retired with a knee injury from playing active sports such as
squash, rugby, and soccer, he has taken up new hobbies in horse eventing and show jumping. In addition, he enjoys

skiing and hill scrambling.

Tim Sammut

, CCIE No. 6642, is a senior network engineer for ExtraTeam, a Cisco partner in San Francisco, Cali-
fornia. Tim has served in key project roles involving technologies from LAN switching to security to SNA integra-
tion and has helped many organizations, ranging from 100 to 130,000 users, make the most of their network
investment. Tim also holds the CISSP, CCIE Security, MCNE, and MCSE certifications.

Brent Stewart

is a Cisco instructor for Global Knowledge. As a Global Knowledge employee, he participated in the
development of ICND, BSCI, BCMSN, BCRAN, and CIT for Internet-based delivery and served as SME (Subject
Matter Expert) for the CD-based ICND and CIT titles. He is currently participating in the BSCI 2.0 update as the lab
development engineer. Prior to working for Global Knowledge, Brent owned an ISP and worked as an IT consultant.
Brent holds the CCNP and CCDP certifications.

Martin Walshaw

, CCIE No. 5629, CCNP, CCDP, is a systems engineer working for Cisco Systems in the enterprise
line of business in South Africa. His areas of specialty are multiservice (voice and video) as well as security, which
keeps him busy both night and day. During the last 12 years or so, Martin has dabbled in many aspects of the IT
industry, ranging from programming in RPG III and Cobol to PC sales. When Martin is not working, he likes to
spend all his available time with his wife, Val, and his son, Joshua. Without their patience, understanding, and sup-
port, projects such as this would not be possible.

Steve Wisniewski

is CCNP certified and has a master of science degree from Stevens Institute of Technology in
telecom management. Steve works for Lehman Brothers as a senior implementation specialist implementing Cisco

switches and routers. He has also previously edited several other Cisco books and authored a book titled

Network
Administration

for Prentice Hall. Steve lives in East Brunswick, New Jersey, with his wife, Ellen.

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Dedication

This book is dedicated to David and Jack, who make everything worthwhile.

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vi

Acknowledgments

All books are the product of a team, and I have been blessed with a dedicated and professional team, whose exper-
tise in their given areas have made this book. Over the course of writing this book and its predecessor, I have come
to think of members of this team as friends as well as colleagues. In particular, I would like to thank John Kane, the
editor in chief, and Drew Cupp, the development editor, who were always there with solutions and support. My
thanks go also to Amy Lewis for her understanding and flexibility. Of course, I thank all the members of the Cisco
Press team helping to bring this book together, including the project editor, Marc Fowler, and the copy editor, Krista
Hansing.
The technical editors, Steve Gifkins, Martin Walshaw, Jorge Aragon, and Steve Wisniewski, were extremely thor-
ough. Their careful attention to detail and constructive advice improved this book immeasurably. I would particu-

larly like to thank Jorge Aragon and Steve Wisniewski who went the extra mile by testing configurations and
producing output screens.
I would also like to thank Wendell Odom, who led me into the art of book writing and has ever generously shared his
expertise.
Of course, I am immensely grateful to my husband, David, for his support, in spite of the long hours demanded by
this book, and to our small son, Jack, for making me laugh and see the joy of life.

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Contents at a Glance

Chapter 1

Cisco Certifications, the BSCI Exam, and This Book’s Features 3

Chapter 2

Managing Scalable Network Growth 27

Chapter 3

IP Addressing 83

Chapter 4

IP Routing Principles 157

Chapter 5

Using OSPF in a Single Area 205

Chapter 6

Using OSPF Across Multiple Areas 283

Chapter 7

Configuring the Integrated IS-IS Protocol 339

Chapter 8

Using EIGRP in Enterprise Networks 423

Chapter 9

Connecting to Other Autonomous Systems—The Basics of BGP-4 483

Chapter 10

Implementing and Tuning BGP for Use in Large Networks 539

Chapter 11

Controlling Routing Updates Across the Network 593

Chapter 12

Scenarios for Final Preparation 665

Appendix A

Answers to Quiz Questions 771

Appendix B

Sample Configurations 843

Appendix C

Glossary 859

Index

903

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Contents

Chapter 1

Cisco Certifications, the BSCI Exam, and This Book’s Features 3

Goals of This Book 4
This Book’s Intended Audience 5
Prerequisites to Reading the Book 5

Overview of Cisco Certifications 6
Exams Required for Certification 8
What’s on the BSCI Exam 9
Cisco BSCI Exam Outline File Excerpts from Cisco.com 9
Author’s Note About Exam Content 12
Topics in This Book 13
How to Use This Book to Pass the Exam 15
I’ve Taken BSCI—Now What? 17
I’ve Taken the Cisco Networking Academy Courses—Now What? 17
I’m New to Internetworking with Cisco, and I Will Not Be Taking the BSCI
Course—Now What? 18
I’ve Learned a Lot About CCNP Topics Through Experience,
But I Will Not Be Taking the BSCI Course—Now What? 19
The Features of This Book 20
Command Syntax Conventions 20
References and Suggested Reading 21
Strategies for The Exam Day 21
Icons Used in This Book 22
Conclusion 24

Chapter 2

Managing Scalable Network Growth 27

How to Best Use This Chapter 27
“Do I Know This Already?” Quiz 28
Foundation Topics 32
Introduction to Corporate Networks—Growth, Scalability, and Congestion 32
Key Requirements of a Network 33
Reliability 33

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Responsiveness 33
Efficiency 34
Adaptability/Serviceability 34
Accessibility/Security 34
Factors That Increase Network Traffic 35
Identifying the Problems Created by Network Congestion 35
Traffic Analysis and Network Design 35
Problems Created by Network Congestion 36
Excessive Traffic 36
Physical Problems of Ethernet 36
Dropped Packets 37
Retransmission of Packets 37
Incomplete Routing Tables 37
Incomplete Server Lists 38
The Spanning-Tree Protocol Breaks 38
Runaway Congestion 39
Symptoms of Congestion 39
Applications Time Out 40
Clients Cannot Connect to Network Resources 40
Network Death Results 40
Creating a Network That Meets the Key Requirements 40
Cisco’s Hierarchical Design 41
Why Scaling Reduces Congestion 41
How Hierarchical Is Hierarchical? 41
The Functions of Each Layer 41

The Access Layer 42
The Distribution Layer 42
The Core Layer 42
General Design Rules for Each Layer 42
IP Access Lists: Alleviating Congestion with Cisco Routers 43
Cisco Proprietary Solutions 44
Managing Network Congestion for IP 44
The Implementation of IP Access Lists 44
IP Access List Overview 45
Standard IP Access Lists 45
Extended IP Access Lists 46
Guidelines for Writing Access Lists 48
Verifying Filter Configuration 49

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Uses of IP Access Lists 51
Security Using Access Lists 51
Controlling Terminal Access 51
Configuration 52
Traffic Control Through Routing Updates 52
Prioritization 54
Types of Prioritization 54
Reducing Network Traffic: Alternatives to Access Lists 55
Null Interface 55
Configuration of Null Interfaces 55
Internet Example 55
Intranet Example 56

CPU Considerations and Additional Methods for Controlling Network Traffic 57
Fast, Autonomous, and Silicon Switching 58
Cisco Express Forwarding 58
Placement of Client/Server 59
Design Principles of a Client/Server Network 59
IP Helper Address 59
Configuration of IP Helper Address 60
Enhanced Interior Gateway Routing Protocol 60
Tunneling into IP 61
Configuration of Tunneling into IP 63
Conclusion 64
Foundation Summary 65
Chapter Glossary 68
Q & A 69
Scenarios 74
Scenario 2-1 74
Scenario 2-2 76
Scenario 2-3 76
Scenario Answers 77
Scenario 2-1 Answers 77
Scenario 2-2 Answers 78
Scenario 2-3 Answers 79

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Chapter 3

IP Addressing 83

How to Best Use This Chapter 83
“Do I Know This Already?” Quiz 84
Foundation Topics 88
Introduction: What Is a Layer 3 Address and How Does It Affect My Life? 88
Case Study 88
The Need for Layer 3 Addressing 88
A Definition of a Layer 3 Address 89
Network Structures and Data Flow 89
The Network and How It Is Addressed 89
A Confusion of Network Terminology 89
Network Terms Explained 90
A Definition of a Layer 3 Network 90
Network Characteristics 90
An IP Address 91
Why IP? 91
IP Network Terminology 91
Network and Host Addressing 92
The Internet Mask 92
The Internet Authoritative Bodies 93
An Example of Bit Allocation in a Network Address 94
The Subnet Mask 94
Where to Place the Network Boundary 94
The Logical AND 95
The AND Operation Rules 95
Familiar Rules in IP Subnetting 96
The Newer Subnet Rules 97
IP Addressing Summary 98
Prefix Routing/CIDR 98
A Definition of Prefix Routing/CIDR 98

Problems with IP Addressing and the Internet 99
CIDR as a Solution 99
Summary of CIDR 100
An Example of the Use of CIDR 100
An Example of CIDR in Use in the Case Study 101
Advantages of Prefix Routing/CIDR 101
Variable-Length Subnet Masks 103
An Example of VLSM 103
Routing Protocols That Support VLSM 103
Rules for VLSM 104
The Advantages of Using VLSM 104

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Case Study: Addressing the Network 105
Bit Allocation, the Subnet Rule, and VLSM 107
Allocating VLSM Addresses 107
Summarization 109
The Advantages of Summarization 112
Reducing the Size of the Routing Table 112
Simplification 112
Hiding Network Changes 112
Network Growth 112
Other Solutions to Address Exhaustion 113
Configuring Summarization 113
Automatic Summarization 113
Manual Summarization 113
Discontiguous Networks 114

Considerations for Summarization with Discontiguous Networks 115
Case Study 115
Alternatives to Summarization 115
Optimizing the IP Address Space 116
Assigning IP VLSM Subnets for WAN Connections 116
Designing IP Networks 118
Keys Points to Remember When Designing an IP Network 120
Private Addresses on the Internet 123
Connecting to the Outside World 125
The Main Features of NAT 127
Conclusion 129
Foundation Summary 130
IP Addressing Summary 130
Summary of CIDR 130
An Example of the Use of CIDR 131
Rules for VLSM 132
Advantages of Summarization 132
Chapter Glossary 133
Q & A 136
Scenarios 142
Scenario 3-1 142
Scenario 3-2 144
Scenario 3-3 144
Scenario Answers 146

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Scenario 3-1 Answers 146

Scenario 3-2 Answers 150
Scenario 3-3 Answers 153

Chapter 4

IP Routing Principles 157

How to Best Use This Chapter 157
“Do I Know This Already?” Quiz 158
Foundation Topics 162
Introduction: What Is a Routing Protocol? 162
Case Study 162
What Is a Routing Protocol? 162
The Definition of a Routing Protocol 163
The Purpose of a Routing Protocol 163
How the Routing Protocol Works 163
Routing and Routed 163
The Network Field 164
The Purpose of the Network Field 164
How the Network Field Is Used 165
The Outgoing Interface Field 165
The Purpose of the Outgoing Interface Field 165
The Metric Field 165
The Next Hop Field 166
The Purpose of the Next Hop Field 166
The show ip route Command 167
How the Routing Table Is Kept Current and Correct 168
Switching Versus Routing 169
The Routing Function 169
The Switching Function 170

Types of Routing Protocols 171
Distance Vector and Link-State Routing Protocols 172
Distance Vector Routing Protocols 173
The Distance Vector Routing Metrics 173
Link-State Routing Protocols 174
The Meaning of Link State 175
Learning About the Network 175
Learning About a Change in the Network 175
Updating Local Network Tables 176
Path Selection 176
Interior and Exterior Routing Protocols 176
Interior Routing Protocols 176
Exterior Routing Protocols 176

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RIP Version 1 177
IGRP 178
OSPF 179
Key Attributes of OSPF 180
Path Selection Between Routing Protocols 181
Administrative Distance 181
Convergence 183
RIPv1 Convergence 183
IGRP Convergence 184
EIGRP Convergence 184
OSPF Convergence 185
Conclusion 185

Foundation Summary 186
Chapter Glossary 189
Q & A 193
Scenarios 198
Scenario 4-1 198
Scenario 4-2 200
Scenario Answers 202
Scenario 4-1 Answers 202
Scenario 4-2 Answers 203

Chapter 5

Using OSPF in a Single Area 205

How to Best Use This Chapter 205
“Do I Know This Already?” Quiz 206
Foundation Topics 211
Introduction: What Is OSPF? 211
Case Study 211
OSPF Terminology 212
OSPF Neighbors 214
OSPF Network Topologies 214
The Hello Packet 216
Adjacent OSPF Neighbors 217
Advantages of Having Neighbors 218
The Designated Router 218

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Backup Designated Routers 218
Why Have Designated Routers? 219
Electing the Designated and Backup Designated Routers 219
How OSPF Builds Its Routing Table 221
A Router Joins the Network 221
A Change in the Network 221
Building the Routing Table on a New OSPF Router 222
Finding Neighbors with the Exchange Process 222
Discovering Routes 224
The Topology Database 226
How the Topology Table Updates the Routing Table 226
A Change in the Network, Maintaining the Topological Database and the Routing
Table 227
Learning a New Route 227
Choosing the Shortest Path First and Building the Routing Table 230
The Metric 230
Information Needed in the Routing Table 231
OSPF Across Nonbroadcast Multiaccess Networks 231
Which Topology to Choose? 232
Subinterfaces 232
Configuring OSPF in a Single Area 234
Required Commands for Configuring OSPF on an Internal Router 234
Enabling The OSPF Routing Protocol 235
The OSPF network Command 235
Options for Configuring OSPF on an Internal Router 237
The Loopback Interface and the Router ID 237
Changing the Default Metric Using the cost Command 238
Determining the Designated Router Using the priority Command 240
A Working Configuration of OSPF on a Single Router 240

Configuring OSPF over an NBMA Topology 242
Configuring OSPF in NBMA Mode 242
Configuring OSPF in Point-to-Multipoint Mode 244
Design Points for the Point-to-Multipoint Mode 244
Configuring OSPF in Broadcast Mode 244
Configuring OSPF in Point-to-Point Mode on a Frame Relay Subinterface 245
Checking the Configuration of OSPF on a Single Router 246
The show ip ospf Command 247
The show ip ospf database Command 248
The show ip ospf interface Command 250
The show ip ospf neighbor Command 252
The show ip protocols Command 255
The show ip route Command 257

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Conclusion 257
Foundation Summary 258
Routing Table 261
Learning a New Route 261
Command Summaries 263
Chapter Glossary 264
Q & A 266
Scenarios 271
Scenario 5-1 271
Scenario 5-2 272
Scenario 5-3 272
Scenario Answers 274

Scenario 5-1 Answers 274
Scenario 5-2 Answers 278
Scenario 5-3 Answers 278

Chapter 6

Using OSPF Across Multiple Areas 283

How to Best Use This Chapter 283
“Do I Know This Already?” Quiz 284
Foundation Topics 289
OSPF in a Multiple Area Network 289
Case Study 289
Why Multiple Areas? 289
How to Determine Area Boundaries 290
Problems with OSPF in a Single Area 290
OSPF Areas 291
OSPF Within an Area 291
Router Types 291
The Link-State Advertisements 293
The ABRs and ASBR Propagation of LSAs 294
OSPF Path Selection Between Areas 295
Calculating the Cost of a Path to Another Area 296
The Path to Another Area 296
The Path to Another AS 296
The Different Types of Areas 297

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Design Considerations in Multiple Area OSPF 299
Summarization 300
The Virtual Link 300
OSPF over an NBMA Network 301
Configuring OSPF on a Multiarea Network 302
Configuration Commands for a Multiarea OSPF Network 302
The network Command 302
The OSPF area range Command for an ABR 304
The OSPF Summarization Command for an ASBR 305
The OSPF Command for a Stub Area 307
The OSPF Command for a Totally Stubby Area 308
The OSPF Command for the Cost of a Default Route Propagated
into the Area 310
Configuring a Virtual Link 311
A Working Configuration of OSPF on a Multiarea Network 314
Checking the Configuration of OSPF on a Multiarea Network 315
The show ip ospf border-routers Command 316
The show ip ospf virtual-links Command 317
Conclusion 318
Foundation Summary 319
OSPF Routers 319
Link-State Advertisements 320
Routing Table Codes 320
Command Summaries 321
Q & A 322
Scenarios 327
Scenario 6-1 327
Scenario 6-2 329
Scenario 6-3 331

Scenario Answers 332
Scenario 6-1 Answers 332
Scenario 6-2 Answers 334
Scenario 6-3 Answers 336

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Chapter 7

Configuring the Integrated IS-IS Protocol 339

How Best to Use This Chapter 339
“Do I Know This Already?” Quiz 340
Foundation Topics 344
Introduction to Integrated IS-IS 344
IS-IS Terminology 345
Similarities Between Integrated IS-IS and OSPF 350
Differences Between OSPF and Integrated IS-IS 351
ISO Addressing for Integrated IS-IS 354
NETs and NSAP 356
Rules of ISO Addressing 356
Example of a NET Address 356
Integrated IS-IS Hierarchical Structure 357
The Level 1 Router 357
The Level 2 Router 358
The Level 1-2 Router 358

Basic Principles of Area Routing 358
Integrated IS-IS Networks and Interfaces 360
Establishing Adjacencies on a Point-to-Point Link 362
Establishing Adjacencies on a Broadcast Link 362
Establishing Adjacencies on a Nonbroadcast Multiaccess (NBMA) Link 363
Network Layer Protocols Used in Integrated IS-IS 363
The Format of the Hello Packet 365
The Format of the LSP 367
The Format of the SNP 368
TLVs 369
Integrated IS-IS Operation 371
The Update Process 372
Sending and Receiving an LSP 372
Determining Whether the LSP in the Database Is Valid 374
The Decision Process 375
Metrics or Cost 376
The Forwarding Process 377
The Receive Process 377
Integrated IS-IS Design Considerations 377
Area Design of Integrated IS-IS Routers 377
Route Summarization 379
Integrated IS-IS NBMA Modeling Solutions in a Switched WAN Network 379

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Configuring Integrated IS-IS 380
Changing the Router from Level 1-2 381
Configuring Summarization 384

Configuring NBMA 386
Verifying the Integrated IS-IS Operation 389
The show clns neighbors Command 391
The show clns interface Command 393
The show isis database Command 396
The show isis database detail Command 397
Troubleshooting the Integrated IS-IS Operation 399
The show isis spf-log Command 400
The debug Commands 401
Conclusion 402
Foundation Summary 403
The ISO Address Format (NSAP) 403
Q & A 406
Scenarios 411
Scenario 7-1 411
Scenario 7-2 412
Scenario Answers 415
Scenario 7-1 Answers 416
Scenario 7-2 Answers 420
Suggested Further Reading 421

Chapter 8

Using EIGRP in Enterprise Networks 423

How to Best Use This Chapter 423
“Do I Know This Already?” Quiz 424
Foundation Topics 429
Introduction: EIGRP in an Enterprise Network 429
Case Study 429

EIGRP Defined 429
Operation of EIGRP 430
How EIGRP Works 431
The Hello Protocol 434
Becoming a Neighbor 434

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The Neighbor Table 434
The Topology Table 436
EIGRP Metrics 438
The DUAL Finite-State Machine 439
Updating the Routing Table in Passive Mode with DUAL 440
Updating the Routing Table in Active Mode with DUAL 441
Choosing a Successor 442
Scaling EIGRP 449
Reasons for a Poorly Scaled EIGRP Network 449
Symptoms of a Poorly Scaled EIGRP Network 449
Solutions to EIGRP Scaling Issues 450
Design Issues Particular to EIGRP 450
The Routing Table 451
Configuring EIGRP 451
The Required Commands for Configuring EIGRP 452
The Optional Commands for Configuring EIGRP 454
Summarization with EIGRP 454
Load Balancing in EIGRP 454
Bandwidth Control 456
EIGRP Defaults in Bandwidth Utilization 456

EIGRP and the Use of the bandwidth Command in WANs 457
Rules in Configuring Bandwidth over an NBMA Cloud 457
The Use of the bandwidth-percent Command 458
Configuring EIGRP for IPX 459
Configuring EIGRP for AppleTalk 461
Verifying the EIGRP Operation 461
The show ip eigrp neighbors Command 462
The show ip eigrp topology Command 463
The show ip eigrp traffic Command 464
The debug Commands 465
Conclusion 466
Foundation Summary 467
Chapter Glossary 468
Q & A 471
Scenarios 476
Scenario 8-1 476
Scenario 8-2 477
Scenario Answers 479
Scenario 8-1 Answers 479
Scenario 8-2 Answers 480

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Chapter 9

Connecting to Other Autonomous Systems—The Basics of BGP-4 483

How to Best Use This Chapter 483

“Do I Know This Already?” Quiz 484
Foundation Topics 488
Introduction: BGP-4 and Communicating with other Autonomous Systems 488
Case Study 488
BGP-4 Operation 489
An Autonomous System Defined 490
Characteristics of BGP-4 491
Overview of the BGP-4 Operation 491
Message Types 492
Synchronization 494
Benefits of the Synchronization Rule 494
CIDR and Route Aggregation 496
BGP-4 Policy-Based Routing 497
Rules of Policy Routing 497
Disadvantages of Policy Routing 499
BGP-4 Attributes 500
The Next-Hop Attribute and a Broadcast Multiaccess Network 503
The Next-Hop Attribute and a Nonbroadcast Multiaccess Network 505
Route Selection Process 505
Basic Configuration Commands to Connect to Another Autonomous System 507
Starting the Routing Process 508
Defining the Networks to Be Advertised 508
Identifying Neighbors and Defining Peer Groups 508
Forcing the Next-Hop Address 508
Disabling Synchronization 509
Aggregating Routes 509
Managing and Verifying the BGP-4 Configuration 510
When to Use BGP-4 511
When Not to Use BGP-4 511
Alternative Methods of Connecting to an ISP 512

Conclusion 513
Foundation Summary 514
The Key Features of BGP-4 514
Chapter Glossary 520
Q & A 522
Scenarios 527

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Scenario 9-1 527
Scenario 9-2 528
Scenario 9-3 529
Scenario Answers 532
Scenario 9-1 Answers 532
Scenario 9-2 Answers 533
Scenario 9-3 Answers 534

Chapter 10

Implementing and Tuning BGP for Use in Large Networks 539

How to Best Use This Chapter 539
“Do I Know This Already?” Quiz 540
Foundation Topics 544
Introduction—Communicating with Other Autonomous Systems with BGP-4 544
Case Study 544
Designing and Configuring a Scalable BGP-4 Network 545
Why Does BGP-4 Require a Fully Meshed Network? 546

Why Is a Fully Meshed Network a Problem? 546
Route Reflectors: The Solution to a Fully Meshed IBGP-4 Network 547
Designs That Avoid a Fully Meshed IBGP-4 Network 548
How Route Reflectors Operate 549
Controlling BGP-4 Traffic 556
How Prefix Lists Work 557
How Prefix Lists Are Processed 558
How to Configure a BGP-4 Prefix List 558
Creating a Prefix List 558
Prefix List Examples 559
Verifying the Prefix List Configuration 559
Redundant Connections into the Internet—Multihoming 560
Multiple Connections into the Internet 561
Receiving Routing Information from the Internet 561
Determining the BGP-4 Path by Tuning the Attributes 564
Commands to Tune BGP-4—Using the Local Preference and Weight Attributes 564
Verifying the Configuration of Attributes 567
Redistribution Between the IGP and BGP-4 570
Advertising Routes from an IGP into BGP-4 571
Advertising Routes from a BGP-4 into an IGP 571
Do ISPs Need to Redistribute Paths from BGP-4 into the IGP? 571
Redistribution from BGP-4 into an IGP in an Organizational Network 572

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Conclusion 573
Foundation Summary 574
Route Reflectors 575

Prefix Lists 576
Routing Updates from Multihomed Connections to the Internet 577
BGP-4 show Commands 578
Chapter Glossary 579
Q & A 580
Scenarios 584
Scenario 10-1 584
Scenario 10-2 585
Scenario 10-3 586
Scenario Answers 588
Scenario 10-1 Answers 588
Scenario 10-2 Answers 589
Scenario 10-3 Answers 590

Chapter 11

Controlling Routing Updates Across the Network 593

How to Best Use This Chapter 593
“Do I Know This Already?” Quiz 594
Foundation Topics 599
Introduction: Controlling the Routing Updates Using Redistribution and Filtering 599
Case Study 599
Redistribution Between Routing Protocols 599
Controlling Routing Updates 601
Reasons to Control Routing Updates 603
The Main Features of Redistribution 604
Default Redistribution Between Routing Protocols 604
Why Use Multiple Routing Protocols? 606
The Reason for Using One Routing Protocol 607

Problems of Configuring Multiple Routing Protocols 607
Path Selection Within a Routing Protocol 608
Path Selection Between Routing Protocols 610
Avoiding Routing Loops When Redistributing 612
Redistribution and Problems with Network Convergence 613

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Configuring Redistribution 614
Generic Steps Required for Redistribution 614
Redistribution Configuration Syntax 615
The Default or Seed Metric 617
When to Configure the Administrative Distance 619
The Passive Interface 621
Static Routes 621
Default Routes 623
Controlling Routing Updates with Filtering 625
Redistribution Examples 627
Redistribution Example 1 628
Redistribution Example 2 629
Redistribution Example 3 632
Policy-Based Routing Using Route Maps 633
Uses for Route Maps 634
Characteristics of Route Maps 634
The Route Map Command Syntax 635
Policy-Based Routing Using Route Maps 636
Characteristics of Policy Routing 637
The Benefits of Policy Based Routing 637

Disadvantages of Policy Routing 638
Criteria by Which Policy-Based Routes Are Determined 638
How Policy-Based Routing Works Using Route Maps 638
The Route Map Statements 639
Configuring Route Maps for Policy Routing 640
The match Commands for Policy Routing with Route Maps 640
Configuration Notes 643
Route Maps, Policy Routing, and Route Switching 643
How to Ensure That Packets Are Switched at Speed (Fast) 643
Verifying, Maintaining, and Troubleshooting the Redistribution Implementation 644
traceroute 644
Extended ping 645
Specific Commands for Monitoring Policy-Routing Configurations 645
Conclusion 646
Foundation Summary 647
Methods of Controlling Routing Updates 647
Automatic Redistribution Between Routing Protocols 648
Default Administrative Distance 649
The Logic Used in Distribute Lists 649
Chapter Glossary 650

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Q & A 652
Scenarios 657
Scenario 11-1 657
Scenario 11-2 658
Scenario Answers 660

Scenario 11-1 Answers 660
Scenario 11-2 Answers 662

Chapter 12

Scenarios for Final Preparation 665

Further Study for Final Preparation 665
How to Best Use This Chapter 666
Scenarios 667
Scenario 12-1 667
Scenario 12-2 668
Scenario 12-3 669
Scenario Answers 671
Scenario 12-1 Answers 671
Scenario 12-2 Answers 673
Scenario 12-3 Answers 675
Three-Part Scenarios 678
Scenario 12-4 678
Scenario 12-4, Part A—Planning 678
Solutions to Scenario 12-4, Part A—Planning 683
Scenario 12-4, Part B—Configuration 687
Solutions to Scenario 12-4, Part B—Configuration 688
Scenario 12-4 Part C—Verification and Questions 689
Solutions to Scenario 12-4, Part C—Verification and Questions 720
Scenario 12-5 724
Scenario 12-5, Part A—Planning 724
Solutions to Scenario 12-5, Part A—Planning 726
Alternative Methods of Transition to Another Routing Protocol 726
Transitioning to EIGRP from the Outer Edges of the Network 727

Summarization in EIGRP 727
Redistribution in EIGRP 727
Preventing Route Loops 728

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