From: Rob Fielding (cisco@xxxxxxxxxxxxx)
Date: Mon Feb 19 2001 - 16:02:29 GMT-3
I'm just reading my e-mail from the weekend, and I didn't see any responses
to this message, so I'm curious if you found the answer to this problem.
Here's why I think R1 is always the exit point (please correct me if I'm
wrong):
1. R1 has only one route to the destination network in Other AS in its
routing table - BGP only picks one route to one destination to install into
the IP routing table..
2. If R1 is the route reflector and R3 and R4 are clients, then the only
route that R3 and R4 will learn is the one that R1 advertises - All IBGP
routers are supposed to have the same information.
If R1 is configured as a route reflector, R3 and R4 should only have IBGP
peering sessions with R1. They should not be peers with R2. -- Anyone
please correct me if I'm wrong on that.
-Rob Fielding
----- Original Message -----
From: "Chuck Larrieu" <chuck@cl.cncdsl.com>
To: "CCIE_Lab Groupstudy List" <ccielab@groupstudy.com>
Sent: Saturday, February 17, 2001 1:33 PM
Subject: BGP Route reflection - route choices
> I haven't had a chance to check this out myself. But a couple of guys in
the
> office were working on a remote rack, and posed this apparent discovery.
> Hope the ASCII art survives and hope I am remembering this correctly.
> Fred - you still monitor this list? If so, correct me if I am wrong) :
>
> |-------Router 2---|----other AS
> 0ther AS----Router_1 | |
> |-------Router 3---|-
> | |
> |-------Router 4----|
>
> this AS has two paths into the same remote AS. BGP learns the router to
> Other AS through both router 1 and router 2.
>
> The route that is reflected to all routers is that of router 1's path to
> Other AS, even though in some cases, router two is the better exit point
> via the IGP routes )
>
> We could not come up with a rationale for this. Artifact? Other issues wit
h
> igp distribution into BGP? Maybe some filters?
>
> Is what they were seeing the result of some design spec within BGP or
> Cisco's implementation of route reflection?
>
> Anyone else seen this?
>
> Chuck
>
> A long shot at passing is better than no shot.
> Right now that's all I got to get me through,
> So I gotta believe!
>
> ( paraphrased from Kathy Baille / Baille and the Boys
> a song from several years ago )
>
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