1 IP Routing Fundamentals 1
1 IP Routing Fundamentals 1
Routing Protocols and Their Placement in the IP Stack 2
Routing Information Protocol 5
About the Contributors 5
Interior Gateway Routing Protocol 6
Enhanced Interior Gateway Routing Protocol 8
Acknowledgments 9
Open Shortest Path First Protocol 9
Exercise 1-1: Routing Protocols 11
Border Gateway Protocol 13
What Is Routing? 15
Key Information for Routers to Route Data 15
Requirements for IP Routing 20
Exercise 1-2: Making IP Routing Work 22
The Two Major Functions of Routing 22
Comparing Distance-Vector Protocols to Link-State Routing Protocols 23
Classful vs. Classless Routing 24
Preface 27
Distance-Vector Routing Protocol Characteristics 29
Introduction 31
Exercise 1-3: Configuring IGRP 33
Link-State Routing Protocol Characteristics 33
Convergence Issues for IP Routing Protocols 35
Two-Minute Drill 38
Q A SelfTest 40
Lab Question 44
SelfTest Answers 45
Lab Answer 47
2 IP Addressing Issues 49
2 IP Addressing Issues 49
Requests for Comments Dealing with IP Addressing Issues 50
RFC 950: IP Subnet Masking 50
RFC 1518: Route Summarization 51
RFCs 1519 and 2050: Classless Interdomain Routing 51
RFC 1631: Network Address Translation 51
RFC 1812: Variable-Length Subnet Masks 51
RFC 1918: Address Allocation for Private Internets 51
IP Address Classes 52
IP Addressing 52
RFC 1918: Private Address Space 54
Subnetting Overview 54
Issues with IP Addressing 60
IP Addressing Choices 62
Exercise 2-1: Subnetting 66
Maximizing IP Address Space Using Variable-Length Subnet Masking 67
Review of Complex Subnetting 68
Variable-Length Subnet Masking 71
Exercise 2-2: Applying VLSM 74
Route Summarization 74
What Is Route Summarization? 74
Considerations for Summarization 76
Rules for Summarization 77
Route Summarization Walkthrough 80
Classless Interdomain Routing 81
CIDR Walkthrough 82
Exercise 2-3: Summarizing 192.168.1.0through 192.168.10.0 83
Exercise 2-4: Creating a CIDR Block 84
Related IP Addressing Commands 85
The IP UNNUMBERED Command 85
The IP HELPER-ADDRESS Command 86
Exercise 2-5: Using the IP HELPER-ADDRESS and IP FORWARD-PROTOCOL Commands to Forward Broadcasts for DNS 90
Two-Minute Drill 93
Q A Self Test 96
Lab Question 101
SelfTest Answers 102
Lab Answer 105
3 OSPF Operation and Configuration for a Single OSPF Area 107
Introduction to OSPF 107
3 OSPF Operation and Configuration for a Single OSPF Area 107
Benefits of OSPF in Comparison to DV Protocols 110
Scalability 110
Flexibility 110
Summarized Advertisements 110
VLSM 111
Incremental Routing Updates 111
Faster Routing Convergence 111
Exercise 3-1: OSPF Benefits 112
Other Benefits 112
Decision Making 112
The Complete Picture 113
How OSPF Discovers, Chooses, and Maintains Routes 113
OSPF Concepts 113
Exercise 3-2: OSPF Timers 115
OSPF Neighbor Relationships 117
Building an OSPF Neighbor Relationship 117
Elements That Must Match for a Neighbor Relationship to Happen 121
OSPF States in Building a Neighbor Relationship 124
OSPF Packet Types 125
LSA Types 129
Shortest Path First Algorithm and Route Selection 134
OSPF LSA Propagation 136
Walk-Through of an LSA Through a Designated Router 141
The OSPF Decision Tree When Receiving an LSA 144
Configuring OSPF in a Single Area 145
The ROUTER OSPF
The NETWORK Command and the Wildcard Mask 146
OSPF Selection of a Router ID 148
Exercise 3-3: Adding Networks to the OSPF Process 148
Trade-offs and the Loopback Address 149
The OSPF COST INTERFACE Command 149
Monitoring and Verifying OSPF Operations 151
The SHOW IP PROTOCOLS Command 151
The SHOW IP ROUTE Command 151
The SHOW IP OSPF INTERFACE Command 152
The SHOW IP OSPF Command 153
The SHOW IP OSPF NEIGHBOR Command 153
The SHOW IP OSPF NEIGHBOR DETAIL Command 154
The DEBUG IP OSPF ADJ Command 154
Exercise 3-4: Listing the Contents of OSPF Databases 155
Two-Minute Drill 157
Q A SelfTest 159
Lab Question 164
SelfTest Answers 165
Lab Answer 168
4 OSPF Behavior and Configuration for Wide Area Networks 171
4 OSPF Behavior and Configuration for Wide Area Networks 171
OSPF Behavior Over a WAN Link 172
OSPF Behavior on an HDLC or PPP Link 173
Exercise 4-1: Basic OSPF Configuration(Single Area) 176
OSPF Configuration and Behavior on a X.25 Link 177
OSPF Configuration and Behavior on Broadcast Networks 178
Topology Choices for an NBMA Network--Specifically, Frame Relay 182
Frame Relay and OSPF 185
OSPF Network Types and NBMA Networks 186
Frame Relay Logical Interfaces vs. Physical Interfaces 192
DR Elections Over NBMA Networks 193
Standard-Based(RFC-Based)Implementation and Operation of OSPF for an NBMA Network 194
The Nonbroadcast Multiaccess Command Option 195
The Point-to-Multipoint Command Option 196
Exercise 4-2: Point-to-Multipoint Networks and OSPF 199
Cisco Proprietary Modes of Implementation and Operation of OSPF for an NBMA Network 200
The NEIGHBOR Command 200
The POINT-TO-MULTIPOINT NONBROADCAST Command 201
The BROADCAST Command 202
The POINT-TO-POINT Command 205
Exercise 4-3: A Point-to-Multipoint Network Without Broadcast Capabilities 207
Two-Minute Drill 210
Q A SelfTest 212
Lab Question 217
SelfTest Answers 219
Lab Answer 222
5 OSPF Operations in a Multiarea Network 225
5 OSPF Operations in a Multiarea Network 225
Scalability Issues with a Single-Area OSPF Network 226
Exercise 5-1: Using a Multiarea Design to Control LSA Traffic 227
Differentiating Among the Types of Areas, Routers, and LSAs in an OSPF Network 228
Functional Descriptions of Routers in an OSPF Network 228
Types of OSPF Link-State Advertisements 230
Types of OSPF Areas 235
LSA Propagation Across a Standard-Area OSPF Network 239
LSA Propagation Across a Stub Area and Standard-Area OSPF Network 240
LSA Propagation Across a Totally Stubby Area and Standard, Area OSPF Network 242
Benefits of OSPF Summarization 243
Exercise 5-2: Troubleshooting Poor Backbone Performance 244
Configuring a Multiarea OSPF Network 245
The OSPF NETWORK Statement 245
The OSPF STUB Command 246
The OSPF ABR SUMMARIZATION Command 247
The OSPF ASBR SUMMARY-ADDRESS Command 248
OSPF Virtual Link 248
Exercise 5-3: Troubleshooting the NETWORK Command 250
Monitoring and Verifying OSPF Operations 250
Exercise 5-4: Troubleshooting Virtual Links 256
Two-Minute Drill 257
Q A SelfTest 259
Lab Question 263
SelfTest Answers 265
Lab Answer 268
6 EIGRP Operations and Configuration 271
6 EIGRP Operations and Configuration 271
Enhanced IGRP Features and Operations 273
EIGRP and Its Major Features 274
Benefits of EIGRP in Comparison to Other IP Routing Protocols 275
EIGRP Terminology 279
Building EIGRP Neighbor Relationships 280
EIGRP Packet Types 283
The Neighbor Table 285
EIGRP Reliability 286
Initial Exchange of Packets 288
EIGRP Route Selection and Metric Calculation 290
Exercise 6-1: EIGRP Metric Calculation 293
The Diffusing Update Algorithm 294
The DUAL Algorithm 295
Feasible Distance 297
Advertised Distance 297
Feasibility Condition 297
Loop Avoidance 297
Exercise 6-2: A DUAL Scenario 298
Basic EIGRP Configuration 300
The ROUTER EIGRP Command 301
The NETWORK Statement 302
Exercise 6-3: Basic EIGRP Configuration 304
Monitoring and Verifying EIGRP Operations 309
Show IP Protocols Command 309
Show IP Route Command 310
SHOW IP EIGRP TOPOLOGY Command 312
SHOW IP EIGRP NEIGHBORS Command 312
The SHOW IP EIGRP EVENTS Command 313
SHOW IP EIGRP TRAFFIC Command 313
The SHOW IP EIGRP INTERFACE Command 314
The DEBUG EIGRP PACKET Command 315
The DEBUG EIGRP FSM Command 316
The DEBUG EIGRP NEIGHBOR Command 316
Exercise 6-4: Troubleshooting EIGRP Operation 317
Two-Minute Drill 322
Q A SelfTest 324
Lab Question 329
SelfTest Answers 331
Lab Answer 335
7 Advanced EIGRP Behavior and Configuration 339
7 Advanced EIGRP Behavior and Configuration 339
Considerations for a Large-Scale Network Using EIGRP 340
Using the Proper Bandwidth for the WAN Interfaces 341
Exercise 7-1: How Metrics Dictate Traffic Paths Using Eigrp 341
Good Addressing 343
Hierarchical Network Design 343
Sufficient Memory on the Router 344
Sufficient Bandwidth on WAN Interfaces to Handle Update Traffic 345
Limiting the Update and Query Range 345
EIGRP IP Address Summarization 346
Disabling Automatic Summarization 347
EIGRP Manual Summarization 347
EIGRP Load Balancing 350
Exercise 7-2: Load Balancing Unequal CIR (Committed Information Rate) 352
EIGRP WAN Optimization 353
Using Bandwidth Statement 353
Limiting the Percentage of Bandwidth EIGRP Uses 355
Point-to-Point Subinterfaces with CIR Per Subinterface 356
Multipoint Circuit with Equal CIR Per Neighbor 356
Multipoint Circuit with Unequal CIR Per Neighbor(Not Recommended) 356
Multipoint Circuit with Unequal CIR Per Neighbor (Recommended) 357
Exercise 7-3: Configuring Frame Relay 357
EIGRP Query Issues 359
The EIGRP Query Process 359
Limiting the Scope of Updates and Query Propagation 362
Two-Minute Drill 365
Q A SelfTest 367
Lab Question 371
SelfTest Answers 372
Lab Answer 375
8 BGP Basic Operations and Configuration 377
8 BGP Basic Operations and Configuration 377
When It Is Appropriate to Use BGP 379
Alternatives to BGP 379
When It Is Not Appropriate to Use BGP 381
Static and Default Routes 383
Exercise 8-1: Reasons for Using and Not Using BGP, and Using a Default Route with BGP 388
Understanding the Border Gateway Protocol 389
What Is an Exterior Routing Protocol? 389
Border Gateway Protocol Version 4 and How It Differs from Its Predecessors 391
An Autonomous System in Relation to BGP 394
The Internet and Routing 396
BGP Terminology and Characteristics 396
BGP Peering 399
What Is a BGP Attribute? 399
BGP Attributes 401
BGP Synchronization 406
BGP Message Types 408
BGP Route Selection Process 414
Exercise 8-2: Identifying Message Formats and Purposes 415
Configuring Basic BGP 417
The ROUTER BGP AUTONOMOUS-SYSTEM Command 417
The NETWORK Statement Under Router BGP 418
The NEIGHBOR Command 419
BGP Basic Configuration 421
The NEIGHBOR NEXT-HOP-SELF Command 421
The NO SYNCHRONIZATION Command 423
The AGGREGATE ADDRESS Command 424
The CLEAR IP BGP Command 427
Exercise 8-3: Resetting Peer Connections 429
BGP Configuration 429
Monitoring BGP Operations 431
The SHOW IP PROTOCOLS Command 431
The SHOW IP ROUTE Command 432
The SHOW IP BGP NEIGHBORS Command 432
The SHOW IP BGP Command 434
The SHOW IP BGP SUMMARY Command 435
The DEBUG IP BGP UPDATES Command 436
Exercise 8-4: Monitoring BGP 439
Two-Minute Drill 441
Q A SelfTest 443
Lab Question 448
SelfTest Answers 450
Lab Answer 453
9 BGP Scalability Issues 459
9 BGP Scalability Issues 459
Scalability Issues and Solutions with iBGP 461
Peering with iBGP Neighbors 461
Contrasting iBGP Behavior to an IGP Method of Propagating Changes 464
Scalability Issues with iBGP Neighbors 465
Route Reflectors as a Scalability Solution 467
Route Reflector Terminology 469
Route Reflector Design and Migration Tips 470
Route Reflector Operations 474
Route Reflector Configuration 476
Exercise 9-1: Route Reflector Redundancy 478
Verifying Route Reflectors 479
Policy Control 481
Defining Prefix Lists 482
Benefits of Prefix Lists 482
Prefix List Operations 483
Configuring Prefix Lists 484
Prefix List Example 487
Exercise 9-2: Prefix List Configuration 487
Verifying Prefix Lists 489
Multihoming 490
Types of Multihoming 490
Default Routes from All Providers 491
Full BGP Table from All Providers 493
Limited BGP Table and Default Route from Each Provider 493
BGP Metric Commands 497
Exercise 9-3: Combining Multihoming Methods 498
A Multihoming BGP Configuration Example 498
Redistribution with IGPs 499
Notifying BGP of Which Networks to Advertise 500
Using the NETWORK Command 501
Redistributing Static Routes into BGP 501
Redistributing Dynamic Routing Protocols into BGP 502
Redistribution of BGP into a Local Routing Protocol 503
Exercise 9-4: Redistribution of BGP into IGP 503
ISP Policy on Redistribution 504
End Autonomous Systems Policy on Redistribution 504
Two-Minute Drill 506
Q A SelfTest 508
Lab Question 512
SelfTest Answers 514
Lab Answer 516
10 Route Filtering and Redistribution 519
10 Route Filtering and Redistribution 519
Selecting and Configuring Ways to Control Route Update Traffic 521
When to Use Redistribution 523
Redistribution Considerations 524
Exercise 10-1: The Case of the Missing Routes 532
Configuring Route Redistribution with a Single Redistribution Gateway 534
Selecting the Core and Edge Routing Protocols 534
Configuring Redistribution into RIP 541
Configuring Redistribution into OSPF 543
Configuring Redistribution into EIGRP 545
EIGRP and OSPF Redistribution Example 546
Configuring the DEFAULT-METRIC Command 546
Configuring the PASSIVE-INTERFACE Command 548
Configuring Static Routes 549
Exercise 10-2: The Correct Filter 557
Configuring Route Redistribution with Multiple Redistribution Gateways 558
Resolving Path Selection Problems Resulting from Redistribution 559
Solutions for Path Selection Problems 560
Using Route Riltering 561
Using Administrative Distance 564
Exercise 10-3: To Loop or Not to Loop? 566
Verifying Route Redistribution 569
The SHOW IP ROUTE Command 569
The TRACEROUTE Command 570
Exercise 10-4: Selective Route Display 570
Two-Minute Drill 575
Q A SelfTest 577
Lab Question 582
SelfTest Answers 583
Lab Answer 586
11 Policy-Based Routing and Route Maps 587
11 Policy-Based Routing and Route Maps 587
Understanding Policy-Based Routing 588
Defining Policy-Based Routing 590
Reasons to Use Policy-Based Routing 592
Types of Policy-Based Routing 593
Exercise 11-1: Creating a Policy Route to Force the Next-Hop Address 595
Defining Route Maps 596
Operations of Route Maps 596
Comparison Between Route Maps and Access Lists 600
Exercise 11-2: Setting the Default Next-Hop IP Address with a Policy Route 601
Creating a Route-Map Command 602
Configuring Route Maps 602
Linking a Route Map to an Interface 606
Conclusion 607
Exercise 11-3: Using IP Policy Routing to Assign a Physical Interface as a Default Gateway 609
Verifying Route Maps 610
The SHOW IP POLICY Command 611
The SHOW ROUTE-MAP Command 611
Exercise 11-4: Using the SHOW IP POLICY and SHOW ROUTE-MAP Commands 612
Two-Minute Drill 614
Q A SelfTest 616
Lab Question 620
SelfTest Answers 621
Lab Answer 624
A About the CD 625
A About the CD 625
CertTrainer 626
System Requirements 626
ExamSim 626
Installing CertTrainer 626
E-Book 628
Saving Scores as Cookies 628
DriveTime 628
Upgrading 629
Help 629
Glossary 631
Glossary 631
Index 703
Index 703