[130276] in North American Network Operators' Group
Re: BGP next-hop
daemon@ATHENA.MIT.EDU (Ingo Flaschberger)
Thu Sep 30 18:02:23 2010
Date: Fri, 1 Oct 2010 00:01:10 +0200 (CEST)
From: Ingo Flaschberger <if@xip.at>
To: Randy Bush <randy@psg.com>
In-Reply-To: <m239sqzzdk.wl%randy@psg.com>
Cc: North American Network Operators Group <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
> i was recently bitten by a cousin of this
>
> research router getting an ebgp multi-hop full feed from 147.28.0.1
> (address is relevant)
>
> it is on a lan with a default gateway 42.666.77.11 (address not
> relevant), so it has
>
> ip route 0.0.0.0 0.0.0.0 42.666.77.11
>
> massive flapping results.
>
> it seems it gets the bgp route for 147.28.0.0/16 and then can not
> resolve the next hop. it would not recurse to the default exit.
>
> of course it was solved by
>
> ip route 147.28.0.0 255.255.0.0 42.666.77.11
>
> but i do not really understand in my heart why i needed to do this.
last time severall years ago on cisco I used a route-map to rewrite the
next-hop.
route-map xx-in permit 10
set ip next-hop 42.666.77.11
route-map xx-out permit 10
set ip next-hop x.x.x.x
neighbor 147.28.0.1 remote-as yyy
neighbor 147.28.0.1 ebgp-multihop 8
neighbor 147.28.0.1 route-map xx-in in
neighbor 147.28.0.1 route-map xx-out out
something like this.
