[c-nsp] Showing alternate BGP paths

Oliver Boehmer (oboehmer) oboehmer at cisco.com
Thu Sep 14 03:36:32 EDT 2006


cisco-nsp-bounces at puck.nether.net <> wrote on :

> Hi,
>     We have a setup with 3 routers running BGP connecting to
> our upstream
> provider and iBGP with the other routers on our local
> network. Usually, when
> the "sh ip bgp xxx.xxx.xxx", is used we can see:
> 
> - the best path
> - other alternative paths with the same local preference
> 
> Is it possible to also view paths with less local preference
> and inactive routes? At the moment we have to run the command on the
router that is
> directly connected to a certain upstream (eBGP) to view
> available paths from them which we can't see from our iBGP routers.
Thanks.

No, BGP only sends the best path to its peers, so if you receive
multiple paths from eBGP peers, the knowledge of the non-best-path is
limited to these nodes.

There are some efforts to change the BGP protocol to send multiple paths
(essentially to allow load-balancing), but this has not been finalized
and implemented anywhere yet (as far as I know)..

	oli



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