Border Gateway Protocol (BGP) is the routing protocol used to exchange routing information across the Internet. It makes it possible for ISPs to connect to each other and for end-users to connect to more than one ISP. BGP is the only protocol that is designed to deal with a network of the Internet's size, and the only protocol that can deal well with having multiple connections to unrelated routing domains. This book is a guide to all aspects of BGP: the protocol, its configuration and operation in an Internet environment, and how to troubleshooting it. The book also describes how to secure BGP, and how BGP can be used as a tool in combating Distributed Denial of Service (DDoS) attacks. Although the examples throughout this book are for Cisco routers, the techniques discussed can be applied to any BGP-capable router. The topics include: * Requesting an AS number and IP addresses * Route filtering by remote ISPs and how to avoid this * Configuring the initial BGP setup * Balancing the available incoming or outgoing traffic over the available connections * Securing and troubleshooting BGP * BGP in larger networks: interaction with internal routing protocols, scalability issues * BGP in Internet Service Provider networks The book is filled with numerous configuration examples with more complex case studies at the end of the book to strengthen your understanding. BGP is for anyone interested in creating reliable connectivity to the Internet. This title focuses on the use of BGP (Border Gateway Protocol) to create reliable Internet connections. BGP makes it possible for ISPs to connect to each other and for customers to connect to more than one ISP. Preface ix The Internet, Routing, and BGP 1(14) Topology of the Internet 2(4) TCP/IP Design Philosophy 6(3) Routing Protocols 9(4) Multihoming 13(2) IP Addressing and the BGP Protocol 15(21) IP Addresses 15(3) Interdomain Routing History 18(1) The BGP Protocol 19(7) Multiprotocol BGP 26(6) Interior Routing Protocols 32(4) Physical Design Considerations 36(25) Availability 36(2) Selecting ISPs 38(1) Bandwidth 39(4) Router Hardware 43(6) Failure Risks 49(2) Building a Wide Area Network 51(3) Network Topology Design 54(7) IP Address Space and AS Numbers 61(14) The Different Types of Address Space 62(4) Requesting Address Space 66(2) Renumbering IP Addresses 68(2) The AS Number 70(1) Routing Registries 71(1) Routing Policy Specification Language 72(3) Getting Started with BGP 75(20) Enabling BGP 75(3) Monitoring BGP 78(2) Clearing BGP Sessions 80(1) Filtering Routes 81(2) Internal BGP 83(4) The Internal Network 87(4) Minimizing the Impact of Link Failures 91(2) eBGP Multihop 93(2) Traffic Engineering 95(33) Knowing Which Route Is Best 96(3) Route Maps 99(1) Setting the Local Preference 100(3) Manipulating Inbound AS Paths 103(2) Inbound Communities 105(3) BGP Load Balancing 108(1) Traffic Engineering for Incoming Traffic 109(1) Setting the MED 109(8) Announcing More Specific Routes 117(3) Queuing, Traffic Shaping, and Policing 120(8) Security and Integrity of the Network 128(19) Passwords and Security 129(2) Software 131(2) Protecting BGP 133(4) Denial-of-Service Attacks 137(10) Day-to-Day Operation of the Network 147(15) The Network Operations Center 147(4) NOC Hardware Facilities 151(1) SNMP Management 152(5) Router Names 157(2) General IP Network Management 159(3) When Things Start to Go Down: Troubleshooting 162(26) Keeping a Clear Head 162(1) Managing the Troubleshooting Process 163(2) Dealing with Service Providers 165(2) Physical and Datalink Layer Problems 167(7) Routing and Reachability Problems 174(6) Black Holes 180(5) DNS Problems 185(3) BGP in Larger Networks 188(25) Peer Groups 188(2) Using Loopback Addresses for iBGP 190(1) iBGP Scaling 191(5) Dampening Route Flaps 196(2) OSPF as the IGP 198(9) Traffic Engineering in the Internal Network 207(2) Network Partitions 209(4) Providing Transit Services 213(15) Route Filters 213(2) Communities 215(6) Anti-DoS Measures 221(3) Customers with Backup Connections 224(1) Providing IPv6 and Multicast 225(3) Interconnecting with Other Networks 228(15) Peering 228(1) Internet Exchanges, NAPs, and MAEs 229(1) Connecting to an Internet Exchange 229(6) Connecting to More Exchange Points 235(2) Rejecting Unwanted Traffic 237(3) IX Subnet Problems 240(1) Talking to Other Network Operators 240(1) Exchange Point Future 241(2) A. Cisco Configuration Basics 243(7) B. Binary Logic, Netmasks, and Prefixes 250(6) C. Notes on the IPv4 Address Space 256(3) Glossary 259(6) Index 265