RFC 2796 (rfc2796) - Page 2 of 11

BGP Route Reflection - An Alternative to Full Mesh IBGP

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