Preface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix
1. The Internet, Routing, and BGP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Topology of the Internet 2
TCP/IP Design Philosophy 6
Routing Protocols 9
Multihoming 13
2. IP Addressing and the BGP Protocol. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
IP Addresses 15
Interdomain Routing History 18
The BGP Protocol 19
Multiprotocol BGP 26
Interior Routing Protocols 32
3. Physical Design Considerations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Availability 36
Selecting ISPs 38
Bandwidth 39
Router Hardware 43
Failure Risks 49
Building a Wide Area Network 51
Network Topology Design 54
4. IP Address Space and AS Numbers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
The Different Types of Address Space 62
Requesting Address Space 66
Renumbering IP Addresses 68
vi | Table of Contents
The AS Number 70
Routing Registries 71
Routing Policy Specification Language 72
5. Getting Started with BGP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Enabling BGP 75
Monitoring BGP 78
Clearing BGP Sessions 80
Filtering Routes 81
Internal BGP 83
The Internal Network 87
Minimizing the Impact of Link Failures 91
eBGP Multihop 93
6. Traffic Engineering. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
Knowing Which Route Is Best 96
Route Maps 99
Setting the Local Preference 100
Manipulating Inbound AS Paths 103
Inbound Communities 105
BGP Load Balancing 108
Traffic Engineering for Incoming Traffic 109
Setting the MED 109
Announcing More Specific Routes 117
Queuing, Traffic Shaping, and Policing 120
7. Security and Integrity of the Network. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128
Passwords and Security 129
Software 131
Protecting BGP 133
Denial-of-Service Attacks 137
8. Day-to-Day Operation of the Network. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147
The Network Operations Center 147
NOC Hardware Facilities 151
SNMP Management 152
Router Names 157
General IP Network Management 159
Table of Contents | vii
9. When Things Start to Go Down: Troubleshooting. . . . . . . . . . . . . . . . . . . . . 162
Keeping a Clear Head 162
Managing the Troubleshooting Process 163
Dealing with Service Providers 165
Physical and Datalink Layer Problems 167
Routing and Reachability Problems 174
Black Holes 180
DNS Problems 185
10. BGP in Larger Networks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188
Peer Groups 188
Using Loopback Addresses for iBGP 190
iBGP Scaling 191
Dampening Route Flaps 196
OSPF as the IGP 198
Traffic Engineering in the Internal Network 207
Network Partitions 209
11. Providing Transit Services. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213
Route Filters 213
Communities 215
Anti-DoS Measures 221
Customers with Backup Connections 224
Providing IPv6 and Multicast 225
12. Interconnecting with Other Networks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228
Peering 228
Internet Exchanges, NAPs, and MAEs 229
Connecting to an Internet Exchange 229
Connecting to More Exchange Points 235
Rejecting Unwanted Traffic 237
IX Subnet Problems 240
Talking to Other Network Operators 240
Exchange Point Future 241
viii | Table of Contents
A. Cisco Configuration Basics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243
B. Binary Logic, Netmasks, and Prefixes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250
C. Notes on the IPv4 Address Space. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256
Glossary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259
Index. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265