User Manual

Enterasys X-Pedition User Reference Manual 197
Chapter 15
BGP Configuration
Guide
BGP Overview
The Border Gateway Protocol (BGP) is an exterior gateway protocol that allows IP routers to
exchange network reachability information. BGP became an internet standard in 1989 (RFC 1105)
and the current version, BGP-4, was published in 1994 (RFC 1771). BGP typically runs between
Internet Service Providers. It is also frequently used by multi-homed ISP customers and large
commercial networks.
Notes:
• BGP management traps are not supported in this release.
• The X-Pedition does not currently follow "Breaking Ties (Phase2)," Section 9.1.2.1 (p. 37-38)
of RFC 1771. Instead, the router follows "Breaking Ties (Phase2)," Section 9.1.2.2 (p. 49-50)
of Draft-ietf-ier-bgp-4-17.
Autonomous systems that wish to connect their networks must agree on a method of exchanging
routing information. Interior gateway protocols such as RIP and OSPF may be inadequate for this
task since they were not designed to handle multi-AS, policy, and security issues. Similarly, using
static routes may not be the best choice for exchanging AS-AS routing information because there
may be a large number of routes, or the routes may change often.
Note: This chapter uses the term Autonomous System (AS) throughout. An AS is defined as a set
of routers under a central technical administration that has a coherent interior routing plan
and accurately portrays to other ASs what routing destinations are reachable by way of it.
In an environment where using static routes is not feasible, BGP is often the best choice for an AS-
AS routing protocol. BGP prevents the introduction of routing loops created by multi-homed and
meshed AS topologies. BGP also provides the ability to create and enforce policies at the AS level,