Publishing Multiple Default Routes into BGP

Unanswered Question
Nov 11th, 2008

We currently have one Internet gateway. We are adding two more. I need to publish these additional default routes into our BGP cloud (we currently use default information-originate to publish the current gateway) and have certain sites use them in preferential order based on geography.

Any ideas on the best way to accomplish this?

The network is a service provider provisioned MPLS network running BGP. Routing varies between OSPF and EIGRP as the IGP at the local sites.

I have this problem too.
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Edison Ortiz Tue, 11/11/2008 - 10:16

Very hard to offer any ideas on this design based on a single post.

This design calls for a careful traffic engineering overview of your network.

The only thing I can tell you that you can modify default traffic behavior in BGP with its known attributes such as AS_PATH Prepending, Local_Pref or even WEIGHT.

Just to be safe, I recommend bringing someone from the outside just to validate the design or any ideas you may have.




mlitka Tue, 11/11/2008 - 10:25

Understood. Thanks for the feedback. I was thinking of tagging the default routes at each gateway location and then using route-maps at the remotes to set local preference based on the tag. They would prefer the tag that is in the same geographic region.

Edison Ortiz Tue, 11/11/2008 - 10:38

Tagging is a very useful mechanism for 'coloring' the traffic within routing protocols. With that said, it works very well during redistribution in most cases but very hard to tell without studying the whole network topology for any gotchas this approach may encounter.

My first recommendation before bringing anyone in is; document everything and become an expert on Visio :) You need all the visual documentation you may have for the entire topology.





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