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BGP and default route

I'm running an MPLS network with BGP. I have three data centers with an Internet exit point in each 1. Site A (GA) 2. Site B (TX) 3. Site C (AZ).

The result I am looking for is to have east offices use Site A (GA) for outbound Internet and west offices use site B (TX) with both east and west failing over to site C (AZ). I can advertise a default route out of site A and B, then the sites will choose the closest Internet point using BGP path selection. For site C I can add an AS-path prepend for failover. But how do I get the sites to fail over to site C rather than site A or B (depending on which fails)?

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Re: BGP and default route

Inject the default route from the desired DataCenters and talk to your MPLS carrier on the best way to influence the closest exit point.

Many carriers simply use the IGP metric to determine the closest exit point - best to check with them.



Re: BGP and default route


There is one approach which providers follow. Please have a look

1- Inject default route from each site (A,B and C)
2- A provider will propogate this default route with specific RT value    via.Export-map in vrf (So every default route will have different RT)
3- So all your offices (east and west) will have three default route.
4- provider here can use import-map to affect routing based on specific RT.

   Say for east sites he can increase local preference for RT received from    site-A and all default routes will have different preference.

   For incoming traffic you can use as-path prepending.



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