BGP routing table won't keep both routes

From: Daniel Fredrick (dfredrick@gmail.com)
Date: Sun Sep 24 2006 - 12:37:37 ART

Here's the BGP topology...

AS254 AS254
(BB1) (BB2)
    | |
    | RR |
  (R1)---------(R5)-----------(R6)
 AS3 AS3 AS3

R5 is the route reflector.

OK... now BB1 and BB2 are sending the same BGP routes. The only difference
is BB1 is sending the same routes is an aspath of "254 253". BB2 is sending
the same routes, but with an aspath of just "254"

OK... so here's my problem. When I do a "show ip bgp" all of the routers
don't show both routes from BB1 and BB2.

R1 shows both routes from BB1 and BB2, with BB2 routes preferred... since it
has a shorter BGP path.

R5 only shows only BB2 routes.

R6 only shows BB2 routes.

So... here comes the confusing part...

When R5 loses R6 as a bgp neighbor and it is down, the routes from BB2
disappear in "show ip bgp" and the routes from BB1 show up in "show ip bgp"

So what could cause R5 and R6 to remove the routes from the bgp table? It
should keep them in there... but just not use them as a preferred route.

Thanks,
Dan

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