Routing TCP/IP

Jeff Doyle, CCIE No. 1919, is vice president of research at Fishtech Labs. Specializing in IP routing protocols, SDN/NFV, data center fabrics, MPLS, and IPv6, Jeff has designed or assisted in the design of large-scale IP service provider and enterprise networks in 26 countries over 6 continents. He worked with early IPv6 adopters in Japan, China, and South Korea, and has advised service providers, government agencies, military contractors, equipment manufacturers, and large enterprises on best-practice IPv6 deployment. He now advises large enterprises on evolving data center infrastructures, SDN, and SD-WAN. Jeff is the author of CCIE Professional Development: Routing TCP/IP, Volumes I and II and OSPF and IS-IS: Choosing an IGP for Large-Scale Networks; a co-author of Software Defined Networking: Anatomy of OpenFlow; and an editor and contributing author of Juniper Networks Routers: The Complete Reference. He also writes for Forbes and blogs for both Network World and Network Computing. Jeff is one of the founders of the Rocky Mountain IPv6 Task Force, is an IPv6 Forum Fellow, and serves on the executive board of the Colorado chapter of the Internet Society (ISOC). Jeff lives in Westminster, Colorado, with his wife Sara and a Sheltie named Max, the Forrest Gump of the dog world. Jeff and Sara count themselves especially fortunate that their four grown children and a growing herd of grandchildren all live within a few miles.

Introduction xxi

Chapter 1 Inter-Domain Routing Concepts 1

Early Inter-Domain Routing: The Exterior Gateway Protocol (EGP) 1

Origins of EGP 2

Operation of EGP 3

EGP Topology Issues 3

EGP Functions 5

Neighbor Acquisition Protocol 6

Neighbor Reachability Protocol 8

Network Reachability Protocol 10

Shortcomings of EGP 15

The Advent of BGP 16

BGP Basics 17

Autonomous System Types 21

External and Internal BGP 22

Multihoming 29

Transit AS Multihoming 30

Stub AS Multihoming 31

Multihoming and Routing Policies 36

Multihoming Issues: Load Sharing and Load Balancing 36

Multihoming Issues: Traffic Control 37

Multihoming Issues: Provider-Assigned Addressing 40

Classless Inter-Domain Routing 41

A Summarization Summary 41

Classless Routing 43

Summarization: The Good, the Bad, and the Asymmetric 47

CIDR: Reducing Class B Address Space Depletion 50

CIDR: Reducing Routing Table Explosion 50

Managing and Assigning IPv4 Address Blocks 54

CIDR Issues: Multihoming and Provider-Assigned Addresses 56

CIDR Issues: Address Portability 58

CIDR Issues: Provider-Independent Addresses 59

CIDR Issues: Traffic Engineering 60

CIDR Approaches Its Limits 62

IPv6 Comes of Age 66

Routing Table Explosion, Again 66

Looking Ahead 68

Review Questions 69

Chapter 2 Introduction to BGP 71

Who Needs BGP? 71

Connecting to Untrusted Domains 71

Connecting to Multiple External Neighbors 74

Setting Routing Policy 79

BGP Hazards 82

Operation of BGP 84

BGP Message Types 85

Open Message 85

Keepalive Message 86

Update Message 86

Notification Message 87

BGP Finite State Machine 87

Idle State 88

Connect State 89

Active State 89

OpenSent State 89

OpenConfirm State 90

Established State 90

Path Attributes 90

ORIGIN Attribute 92

AS_PATH Attribute 92

NEXT_HOP Attribute 97

Weight 100

BGP Decision Process 100

BGP Message Formats 103

Open Message 104

Update Message 105

Keepalive Message 108

Notification Message 108

Configuring and Troubleshooting BGP Peering 110

Case Study: EBGP Peering 110

Case Study: EBGP Peering over IPv6 114

Case Study: IBGP Peering 118

Case Study: Connected Check and EBGP Multihop 127

Case Study: Managing and Securing BGP Connections 136

Looking Ahead 142

Review Questions 143

Configuration Exercises 144

Troubleshooting Exercises 145

Chapter 3 BGP and NLRI 155

Configuring and Troubleshooting NLRI in BGP 155

Injecting Prefixes with the network Statement 156

Using the network mask Statement 160

Injecting Prefixes with Redistribution 162

NLRI and IBGP 167

Managing Prefixes in an IBGP Topology 168

IBGP and IGP Synchronization 179

Advertising BGP NLRI into the Local AS 182

Redistributing BGP NLRI into the IGP 182

Case Study: Distributing NLRI in a Stub AS with IBGP 184

Distributing NLRI in a Stub AS with Static Routes 193

Advertising a Default Route to a Neighboring AS 196

Advertising Aggregate Routes with BGP 198

Case Study: Aggregation Using Static Routes 199

Aggregation Using the aggregate-address Statement 201

ATOMIC_AGGREGATE and AGGREGATOR Attributes 207

Using AS_SET with Aggregates 210

Looking Ahead 218

Review Questions 218

Configuration Exercises 219

Troubleshooting Exercises 223

Chapter 4 BGP and Routing Policies 237

Policy and the BGP Database 238

IOS BGP Implementation 249

InQ and OutQ 249

IOS BGP Processes 251

NHT, Event, and the Open Processes 256

Table Versions 258

Managing Policy Changes 267

Clearing BGP Sessions 268

Soft Reconfiguraton 269

Route Refresh 274

Route Filtering Techniques 279

Filtering Routes by NLRI 280

Case Study: Using Distribute Lists 280

Route Filtering with Extended ACLs 292

Case Study: Using Prefix Lists 293

Filtering Routes by AS_PATH 304

Regular Expressions 304

Literals and Metacharacters 305

Delineation: Matching the Start and End of Lines 306

Bracketing: Matching a Set of Characters 306

Negating: Matching Everything Except a Set of Characters 306

Wildcard: Matching Any Single Character 307

Alternation: Matching One of a Set of Characters 307

Optional Characters: Matching a Character That May or May Not Be There 307

Repetition: Matching a Number of Repeating Characters 307

Boundaries: Delineating Literals 308

Putting It All Together: A Complex Example 308

Case Study: Using AS-Path Filters 309

Case Study: Setting Policy with Route Maps 314

Filter Processing 322

Influencing the BGP Decision Process 323

Case Study: Administrative Weights 325

Case Study: Using the LOCAL_PREF Attribute 334

Case Study: Using the MULTI_EXIT_DISC Attribute 343

Case Study: Prepending the AS_PATH 366

Case Study: Administrative Distances and Backdoor Routes 372

Controlling Complex Route Maps 379

Continue Clauses 380

Policy Lists 383

Looking Ahead 386

Review Questions 386

Configuration Exercises 388

Troubleshooting Exercises 392

Chapter 5 Scaling BGP 401

Scaling the Configuration 402

Peer Groups 403

Peer Templates 413

Session Templates 414

Policy Templates 419

Communities 425

Well-Known Communities 426

Arbitrary Communities 434

Using the AA:NN Format 443

Expanded Community Lists 445

Adding and Deleting Communities 460

Extended Community Lists 472

Scaling BGP Functions 478

Route Flap Dampening 479

Outbound Route Filters (ORF) 486

Next-Hop Tracking 496

Fast External Fallover 509

Bidirectional Forwarding Detection (BFD) 512

BGP Prefix Independent Convergence (PIC) 523

ADD-PATHS Capability 528

Graceful Restart 538

Maximum Prefixes 540

Tuning BGP CPU 552

Tuning BGP Memory 556

BGP Transport Optimization 563

Optimizing TCP 563

Optimizing BGP Update Generation 568

Optimizing TCP ACK Message Receipt 568

Scaling the BGP Network 569

Private AS Numbers 569

4-Byte AS Numbers 574

IBGP and the N-Squared Problem 575

Confederations 576

Route Reflectors 592

Looking Ahead 606

Review Questions 607

Configuration Exercises 608

Troubleshooting Exercises 612

Chapter 6 Multiprotocol BGP 615

Multiprotocol Extensions to BGP 616

MBGP Support for the IPv6 Address Family 618

Configuring MBGP for IPv6 619

IPv4 and IPv6 Prefixes over an IPv4 TCP Session 620

Upgrading IPv4 BGP Configurations to the Address Family Format 629

IPv4 and IPv6 over an IPv6 TCP Connection 631

Dual Stack MBGP Connection 642

Multihop Dual Stack MBGP Connection 647

Mixed IPv4 and IPv6 Sessions 650

Multiprotocol IBGP 654

Case Study: Multiprotocol Policy Configuration 666

Looking Ahead 705

Review Questions 705

Configuration Exercises 706

Question 1: 707

Troubleshooting Exercises 709

Chapter 7 Introduction to IP Multicast Routing 713

Requirements for IP Multicast 716

IPv4 Multicast Addresses 717

IPv6 Multicast Addresses 721

Group Membership Concepts 724

Joining and Leaving a Group 726

Join Latency 726

Leave Latency 727

Group Maintenance 728

Multiple Routers on a Network 728

Internet Group Management Protocol (IGMP) 729

IGMPv2 Host Functions 730

IGMPv2 Router Functions 731

IGMPv1 733

IGMPv3 735

IGMP Message Format 736

Multicast Listener Discovery (MLD) 742

IGMP/MLD Snooping 745

Cisco Group Management Protocol (CGMP) 749

Multicast Routing Issues 753

Multicast Forwarding 754

Multicast Routing 756

Sparse Versus Dense Topologies 757

Implicit Joins Versus Explicit Joins 758

Source-Based Trees Versus Shared Trees 760

Source-Specific Multicast (SSM) 761

Multicast Scoping 763

TTL Scoping 763

Administrative Scoping 765

Looking Ahead 766

Recommended Reading 766

Review Questions 766

Configuration Exercises 768

Chapter 8 Protocol Independent Multicast 771

Introduction to Protocol Independent Multicast (PIM) 771

Operation of Protocol Independent Multicast-Dense Mode (PIM-DM) 773

PIM-DM Basics 773

Prune Overrides 779

Unicast Route Changes 782

PIM-DM Designated Routers 782

PIM Forwarder Election 782

Operation of Protocol Independent Multicast-Sparse Mode (PIM-SM) 785

PIM-SM Basics 786

Finding the Rendezvous Point 787

Bootstrap Protocol 787

Auto-RP Protocol 789

Embedded RP Addresses 790

PIM-SM and Shared Trees 793

Source Registration 796

PIM-SM and Shortest Path Trees 803

PIMv2 Message Formats 808

PIMv2 Message Header Format 809

PIMv2 Hello Message Format 810

PIMv2 Register Message Format 811

PIMv2 Register Stop Message Format 812

PIMv2 Join/Prune Message Format 812

PIMv2 Bootstrap Message Format 814

PIMv2 Assert Message Format 815

PIMv2 Graft Message Format 816

PIMv2 Graft-Ack Message Format 816

Candidate-RP-Advertisement Message Format 817

Configuring IP Multicast Routing 817

Case Study: Configuring Protocol Independent Multicast-Dense Mode (PIM-DM) 819

Configuring Protocol Independent Multicast-Sparse Mode (PIM-SM) 828

Case Study: Statically Configuring the RP 829

Case Study: Configuring Auto-RP 837

Case Study: Configuring Sparse-Dense Mode 845

Case Study: Configuring the Bootstrap Protocol 849

Case Study: Multicast Load Sharing 856

Troubleshooting IP Multicast Routing 863

Using mrinfo 865

Using mtrace and mstat 867

Looking Ahead 872

Recommended Reading 872

Review Questions 873

Configuration Exercises 873

Troubleshooting Exercises 876

Chapter 9 Scaling IP Multicast Routing 881

Multicast Scoping 881

Case Study: Multicasting Across Non-Multicast Domains 885

Connecting to DVMRP Networks 888

Inter-AS Multicasting 891

Multiprotocol Extensions for BGP (MBGP) 894

Operation of Multicast Source Discovery Protocol (MSDP) 896

MSDP Message Formats 898

Source Active TLV 898

Source Active Request TLV 899

Source Active Response TLV 900

Keepalive TLV 900

Notification TLV 900

Case Study: Configuring MBGP 902

Case Study: Configuring MSDP 908

Case Study: MSDP Mesh Groups 913

Case Study: Anycast RP 917

Case Study: MSDP Default Peers 923

Looking Ahead 926

Review Questions 926

Configuration Exercise 927

Chapter 10 IPv4 to IPv4 Network Address Translation (NAT44) 931

Operation of NAT44 932

Basic NAT Concepts 932

NAT and IP Address Conservation 934

NAT and ISP Migration 937

NAT and Multihomed Autonomous Systems 938

Port Address Translation (PAT) 940

NAT and TCP Load Distribution 942

NAT and Virtual Servers 944

NAT Issues 944

Header Checksums 945

Fragmentation 945

Encryption 945

Security 946

Protocol-Specific Issues 946

ICMP 947

DNS 948

FTP 951

SMTP 953

SNMP 953

Routing Protocols 953

Traceroute 953

Configuring NAT44 955

Case Study: Static NAT 955

NAT44 and DNS 962

Case Study: Dynamic NAT 964

Case Study: A Network Merger 969

Case Study: ISP Multihoming with NAT 975

Port Address Translation 980

Case Study: TCP Load Balancing 982

Case Study: Service Distribution 984

Troubleshooting NAT44 986

Looking Ahead 988

Review Questions 989

Configuration Exercises 989

Troubleshooting Exercises 991

Chapter 11 IPv6 to IPv4 Network Address Translation (NAT64) 995

Stateless IP/ICMP Translation (SIIT) 997

IPv4/IPv6 Header Translation 999

ICMP/ICMPv6 Translation 1002

Fragmentation and PMTU 1005

Upper-Layer Header Translation 1006

Network Address Translation with Port Translation (NAT-PT) 1007

Operation of NAT-PT 1008

Configuring NAT-PT 1010

Why Is NAT-PT Obsolete? 1029

Stateless NAT64 1031

Operation of Stateless NAT64 1031

Configuration of Stateless NAT64 1036

Limitations of NAT64 1038

Stateful NAT64 1038

Operation of Stateful NAT64 1038

Configuration of Stateful NAT64 1041

Limitations of Stateful NAT64 1043

Looking Ahead 1043

Review Questions 1044

Configuration Exercise 1044

Configuration Exercise Premise 1045

Appendix A Answers to Review Questions 1047

Appendix B (online) Answers to Configuration Exercises

Appendix C (online) Answers to Troubleshooting Exercises

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