BGP peer not receiving some routes

Unanswered Question
Nov 6th, 2009
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We have an MPLS network with 20 or so peers using BGP for connectivity from site to site.

When the BGP scheme was originally set up, two sites were given the same AS number. This has not been a problem, until now.

I am trying to filter the route tables on a few of the peers, including the default route that is being advertised.

To do this, I need to distribute some routes that these peers need to get to.

The problem is some of these routes are being advertised from the site that has the same AS number.

The peer that I am trying to filter, is not receiving any of the above routes from the identical AS number.

Is there any way to get around this, other than getting with the provider to change the AS number on one of the branches with identical AS numbers?

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Overall Rating: 5 (3 ratings)
wilson_1234_2 Fri, 11/06/2009 - 07:36
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Thanks Edison, much appreciated.

That has always bothered me when I discovered it, I knew it would come back to haunt me.

This will allow me to workaround in the meantime, thanks for the reply.

wilson_1234_2 Fri, 11/06/2009 - 08:14
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The allowas-in will allow the PE router send the routes to my CE router that has the same AS as another one of my branches with the same AS?

It is not the PE router that has the same AS, but another one of my branches, which also peers to the PE router.

For example, both branches have AS 65011 and both of them peer to PE in AS 65000

If I configure "nei [PE Router ip address] allowas-in" on branch 2 router (AS 65011), I will receive routes from branch 1 (AS 65011) to branch 2 router?

Edison Ortiz Fri, 11/06/2009 - 08:29
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Yes, the PE will send the routes. Your BGP router will drop the routes as they have the same AS and loop avoidance takes place. 'Allowas-in' knob allows you to disable this loop avoidance so proceed with care...




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