RFC 2796 (rfc2796) - Page 3 of 11
BGP Route Reflection - An Alternative to Full Mesh IBGP
Alternative Format: Original Text Document
RFC 2796 BGP Route Reflection April 2000
+-------+ +-------+
| | IBGP | |
| RTR-A |--------| RTR-B |
| | | |
+-------+ +-------+
\ /
IBGP \ ASX / IBGP
\ /
+-------+
| |
| RTR-C |
| |
+-------+
Figure 1: Full Mesh IBGP
In ASX there are three IBGP speakers (routers RTR-A, RTR-B and RTR-
C). With the existing BGP model, if RTR-A receives an external route
and it is selected as the best path it must advertise the external
route to both RTR-B and RTR-C. RTR-B and RTR-C (as IBGP speakers)
will not re-advertise these IBGP learned routes to other IBGP
speakers.
If this rule is relaxed and RTR-C is allowed to advertise IBGP
learned routes to IBGP peers, then it could re-advertise (or reflect)
the IBGP routes learned from RTR-A to RTR-B and vice versa. This
would eliminate the need for the IBGP session between RTR-A and RTR-B
as shown in Figure 2 below.
+-------+ +-------+
| | | |
| RTR-A | | RTR-B |
| | | |
+-------+ +-------+
\ /
IBGP \ ASX / IBGP
\ /
+-------+
| |
| RTR-C |
| |
+-------+
Figure 2: Route Reflection IBGP
The Route Reflection scheme is based upon this basic principle.
Bates, et al. Standards Track
