Re: [nsp] A question regarding BGP next-hop reachability.

From: Robert E. Seastrom (rs@seastrom.com)
Date: Sun Jun 17 2001 - 08:58:43 EDT


For instance (assuming the link between you and the default router is
192.168.0.0/30, you are .2 default is .1):

router bgp 65000
 neighbor 192.168.0.1 remote-as 65000
 neighbor 192.168.0.1 description default router ibgp session
 neighbor 192.168.0.1 route-map jam-next-hop in

route-map jam-next-hop permit 10
 set ip next-hop 192.168.0.1

That should do it -- now all your next-hops are belong^H^H^H^H^H^H to
an address on a connected subnet. :)

It's worth noting that 12.0(S) seems to have "set ip next-hop peer-address"
too, which is the receiving side equivalent of "next-hop-self".

                                        ---Rob

George Robbins <grr@shandakor.tharsis.com> writes:

> Well, reachable via the default gateway is a different statement than
> there being a valid route to the next hop. You should arrange things
> such that there is a valid route from your router to each of the
> next-hops that the route-reflector can offer, at least the ones that
> you want to listen to vs. default routing or bouncing thru the route
> reflector.
>
> George
>
> > From cisco-nsp-request@puck.nether.net Sun Jun 17 04:28:22 2001
> > Resent-Date: Sun, 17 Jun 2001 04:28:15 -0400
> > Received-Date: Sun, 17 Jun 2001 04:23:50 -0400
> > X-Authentication-Warning: nvt.netvision.net.il: elijah owned process doing -bs
> > Date: Sun, 17 Jun 2001 11:23:47 +0300 (IDT)
> > From: Elijah Kagan <elijah@netvision.net.il>
> > To: cisco-nsp@puck.nether.net
> > Subject: [nsp] A question regarding BGP next-hop reachability.
> > Resent-From: cisco-nsp@puck.nether.net
> > X-Mailing-List: <cisco-nsp@puck.nether.net> archive/latest/6854
> > X-Loop: cisco-nsp@puck.nether.net
> > Precedence: list
> > Resent-Sender: cisco-nsp-request@puck.nether.net
> >
> >
> > Suppose there is a router (a Cisco router, of course) that learns nothing
> > but a default gateway from its IGP. It also has an iBGP session with its
> > default router and receives the full Internet routing table. The default
> > router acts as a route-reflector.
> >
> > Now here is the problem. The next-hop of every BGP prefix it learns is
> > reachable via IGP's default gateway, but for some reason it is not good
> > enough, BGP marks it as inaccessible and disregards the prefix.
> >
> > This situation could appear in L1 router that learns a prefix originating
> > form a different IS-IS area.
> >
> > Please advise....
> >
> > -- elijah
> >
> >
> >



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