[c-nsp] IBGP Routing Trouble on 6509

[Oliver Boehmer (oboehmer)]

Richard J. Sears <> wrote on Tuesday, June 27, 2006 11:42 PM:

> Hi Oli -
> 
> 
> Here is the sh ip bg on that address space - I just cut it to save a
> bit of space...
> 
> 
> AR01#show ip bgp 4.36.116.0
> BGP routing table entry for 4.36.116.0/24, version 11742246
> Paths: (3 available, best #2, table Default-IP-Routing-Table)
>   Advertised to update-groups:
>      5          8
>   7911 174 21889, (received & used)
>     206.71.160.254 (metric 11) from 206.251.233.253 (206.251.233.253)
>       Origin IGP, localpref 140, valid, internal
>       Community: 6130:17159
>       Originator: 206.251.233.42, Cluster list: 206.251.233.0
>   7911 174 21889, (received & used)
>     206.71.160.254 (metric 11) from 206.251.233.245 (209.112.240.1)
>       Origin IGP, localpref 140, valid, internal, best
>       Community: 6130:17159
>       Originator: 206.251.233.42, Cluster list: 206.251.233.0
>   7911 174 21889, (received & used)
>     206.71.160.254 (metric 11) from 206.251.233.249 (206.251.233.249)
>       Origin IGP, localpref 140, valid, internal
>       Community: 6130:17159
>       Originator: 206.251.233.42, Cluster list: 206.251.233.0
> 
> 
> 
> So my question is that if I show the route in the bgp table and in the
> ip routing table and its all correct yet the switch is sending traffic
> to someplace its not supposed to, then could there be an issue with
> the RIB or FIB tables..?

Well, the RIB looked fine (didn't it?), so it could be some problem with
the FIB (which is used for forwarding). So "show ip cef <prefix>" and
"show mls cef .." need to be looked at to see what's happening.

> Could this be an issue of running out of FIB TCAM max routes..? (Mine
> still set to default)..?

not sure, if the box runs out of tcam space, it should software-switch
part of the traffic.. it could also be an inconsistency between RIB and
FIB or between software-FIB and hardware-FIB. Not sure, would need to
take a look at the FIB/HW-FIB next time it happens.. the URL I sent
should provide some guidance.

	oli