RFC 2796 (rfc2796) - Page 2 of 11
BGP Route Reflection - An Alternative to Full Mesh IBGP
Alternative Format: Original Text Document
RFC 2796 BGP Route Reflection April 2000
This scaling problem has been well documented and a number of
proposals have been made to alleviate this [2,3]. This document
represents another alternative in alleviating the need for a "full
mesh" and is known as "Route Reflection". This approach allows a BGP
speaker (known as "Route Reflector") to advertise IBGP learned routes
to certain IBGP peers. It represents a change in the commonly
understood concept of IBGP, and the addition of two new optional
transitive BGP attributes to prevent loops in routing updates.
This document is a revision of RFC 1966 [4], and it includes editorial
changes, clarifications and corrections based on the deployment
experience with route reflection. These revisions are summarized in
the Appendix.
2. Design Criteria
Route Reflection was designed to satisfy the following criteria.
o Simplicity
Any alternative must be both simple to configure as well as
understand.
o Easy Transition
It must be possible to transition from a full mesh
configuration without the need to change either topology or AS.
This is an unfortunate management overhead of the technique
proposed in [3].
o Compatibility
It must be possible for non compliant IBGP peers to continue be
part of the original AS or domain without any loss of BGP
routing information.
These criteria were motivated by operational experiences of a very
large and topology rich network with many external connections.
3. Route Reflection
The basic idea of Route Reflection is very simple. Let us consider
the simple example depicted in Figure 1 below.
Bates, et al. Standards Track