[c-nsp] Strange behavior in sh ip bgp neighbors x.y.z.wadvertised-routes

[Oliver Boehmer (oboehmer)]

Diogo Montagner <> wrote on Friday, June 15, 2007 10:57 PM:

> Hello all,
> 
> considering the scenario:
> 
> router-AS1 <--> router-AS2
> 
> In this AS1 bgp neighbor configuration I have a outbound policy that
> modify the attributes of routes.
> 
> In this route-map OUT, I have a instance where I insert a route
> prepend. When I search for this route using the AS2 looking glass I
> can see the prepend, but when I issue the "sh ip bgp neighbor x.y.z.w
> advertised-routes" in router-AS1 I cannot find this prepend. This same
> behavior is observed in others BGP attributes like metric, local
> preference, etc.

yes, this is expected.

> Our support said that the command "sh ip bgp neighbors x.y.z.w adv"
> show the routes before it cross the outbound policer. But the weird
> thing is, if in this outbound policy I put a deny instance for don't
> advertise the route to AS2, the route disappear from the output of
> command "sh ip bgp nei x.y.z.w adv".

Well, the command shows all the prefixes which have been sent to the
specific peer, but it uses the attributes as present in the local BGP
table when we display the list. Any outbound modification of the BGP
attributes (either explicitly through a route-map, or implicitly through
BGP, for example next-hop change for external updates) are not shown.

> Is there a command that shows the routes after it crosses the
> outbound policer ? 

I think only "debug ip bgp update .." shows the routes as they're being
sent.

	oli