Hi Michael,
it seems as I look more and more into this, mind you I’m no bgp expert, I think
what is happening might be normal iBGP behavior.
Heres how the network is setup.
Router A (customer) which connects to router B (my router) . Router B is
connection to router C (my 2nd router) over iBGP.
My BGP customer advertises 5 routes. The router directly connected to my
customer’s bgp router (Router A) shows all 5 routes when I do a (sh ip bgp
sum).
Router C (my 2nd router iBGP) only shows these 5 router when I type “show ip
bgp sum” for about a 1:15 to 1:30 minutes then the routes disappear from
State/PfxRcd.
When I do a show ip bgp on router B for one of the received routes from router
A (cust router) it’s says:
Paths: (2 available, best #1, table Default-IP-Routing-Table)
Multipath: iBGP
Not advertised to any peer
The second best route being from my customer (router A) and the 1st best route
being from Router C (my second iBGP router)
Now on Router C, where I’m confused when I do show ip bgp for the same route I
see.
Paths: (2 available, best #1, table Default-IP-Routing-Table)
Advertised to update-groups:
1
Both routes being from my two up streams on that router.
My confusion is when I do a show ip bgp sum <router B’s neighbor address> I see
5 routes under State/PfxRcd then after a minute or two they disappear.
Is this normal ibgp behavior? Are the router listed under State/PfxRcd only
routes that are inserted in the routing table?
From: Michael K. Smith - Adhost [mailto:[email protected]]
Sent: Friday, February 06, 2009 3:47 PM
To: Paul A
Cc: [email protected]
Subject: RE: [c-nsp] learned routes disappear
Hello Paul:
>
> Paul A wrote:
> > Hi, I'm having a bgp issue I can't figure out and hoping someone has ran
> > into this.
> >
> >
> >
> > I have two routers, router A and router B doing bgp.
> >
> >
> >
> > Router A is advertising 5 routes to router B, when the session 1st comes
> up,
> > router B has 5 routes received from router A. After 1:15 min the learned
> > routes on router B disappear.
> >
> >
How are the routes getting into BGP? Are the coming in via tie-down routes in
the IGP somewhere? Could it be that you have an IGP failure of some sort such
that the routes are being withdrawn legitimately?
Regards,
Mike
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