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Re: BGP on NBMA posted 11/05/2002
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Hi all/Pete,

It looks like this is slowly being solved.

#1-First it was a problem with my layer 2 connectivity.  I had my frame map
statements entered incorrectly on my NBMA network

#2- I appear to have a loop in my routing table caused by a triple
redistribution problem on one of the routers and no distribute list to stop
the feedback  :(  .

3- curious still as to your comment on the next hop self pertaining to IBGP
and not EBGP.  I specifically got the next hop self from the BGP Case Study
#2 on CCO about multiple ASs in an NBMA network.  Did I read that
incorrectly?  Are you saying that you only use the next hops self command
w/in IBGP?  What do you mean by reset next hop for EBGP?

Thanks,

JT

----- Original Message -----
From: "Peter van Oene" <pvo@xxxxxxxxxxxx>
To: <ccielab@xxxxxxxxxxxxxx>
Sent: Tuesday, November 05, 2002 5:48 AM
Subject: Re: BGP on NBMA


> At 11:23 AM 11/4/2002 -0800, Jim Terry wrote:
> >Hi all,
> >
> >I have another BGP question on an NBMA network.
>
> BGP runs over TCP and so long as you have IP reach ability, the L2
topology
> shouldn't matter
>
> >All spokes and hub are running OSPF and there is proper connectivity.
> >The hub is one AS and the spokes are in a different AS.
>
> I must say this is a bizarre setup.
>
> >I can ping the loopbacks for all OSPF advertised interfaces but cannot
ping
> >the loopbacks that are advertised in BGP with the network command.  It
does
> >not matter if I am pinging spoke to spoke(same AS) or spoke to
hub(different
> >AS)
>
> As with your last example, did you verify:
>
>          a) appropriate routes are in the bgp table (show ip bgp)
>          b) BGP next-hop is reachable
>          c) appropriate routes are in the local rib (show ip route)
>
> Keep in mind this is bi-directional and you'll need to make sure that your
> destinations can respond to the source of your pings.
>
>
> >I do have in BGP the next-hop-self from the hub to one spoke.  That one
> >spoke is the route-reflector for the other spokes.  Spoke to spoke
> >connectivity is only via the serial links in the NBMA through the hub.
>
> Next-hop Self is an IBGP function and does  not relate to EBGP peering.
In
> EBGP, you must reset next-hop.   Are your spoke to spoke peerings
> established?  What do the adj-rib in/outs look like (show ip bgp neighbor
> x.x.x.x. advertised-routes / received routes)
>
>
> >Does anyone have any ideas?
>
> You really need to step through a logical debugging process here much like
> you would any reach ability problems.  BGP adds the additional steps of
> verifying peering, route advertisement / reception, BGP next-hop
> resolution, and sync if you have it enabled.
>
> >JT
>
> Pete