Vikas, We monitor our peer sessions via the BGP3 MIB where we can. But we can't on our Ciscos because they haven't implemented the BGP3 MIB (or any BGP MIB). Daniel ~~~~~~ --------
Dunno if this has happened to others before, but in case not:
I have a setup where 3 routers (ciscos, running 9.1.x if that's important) are running IBGP.
A---------B-----------C | ext-net
Router-A peers with 'B' & 'C', Router-B peers with B & C and C with B&A (a full IBGP mesh). Router A is an exit/border router. In addition to BGP, the routers run IGRP. The BGP routes are kept separate from the IGRP routes.
For whatever reason (not a configuration error), the BGP session between A-B died but not between A-C, B-C.
The result was that C 'knew' via the BGP session with A, that to get to external network 'ext-net', it should send traffic to A. It does the IGRP lookup to get to A, and sends the traffic to 'B'. However, since B did not have a BGP session with A, it did not know how to get to the ext-net (in the real case, B was sending traffic back to C since the default route was via C).
A potential disaster!! I realize that the problem was the unexpected 'lost' BGP session between A-B, but are we sure that in a more complicated topology, something similar cannot happen ?
What really make me worried is that there doesn't seem to be way to detect this kind of a problem easily.. how do others monitor their BGP sessions ?
-vikas vikas@jvnc.net