Three default routes out of WAN - how to route out via location

[michael.mastropaolo]

I will try to keep this simple.  We are looking to redo our WAN which peers with another WAN that we own (different ASNs).  We'll call these WAN1 and WAN2.  These span across the nation for arguments sake.  We have 3 eBGP peers throughout the nation.  

If WAN2 were to advertise a default route to WAN1, is there a way to have it so edge gear will route out based on location?  For example, lets say one peer is in NYC and another one in Denver.  A server in Florida would route out the NYC default route because it's the best path, where as a server in California will route out the Denver one, but also provide redundancy should one of them fail.

As mentioned, and i'm not sure if this complicates things, but we need to have 3 peers.

Any help would be appreciated.  Thank you.

[Deivid85_]

Hello Michael,

I think you are looking a solution similar to this one:

http://www.davidsudjiman.info/2007/12/17/bgp-why-we-need-to-create-static-route-to-advertise-a-network/

You can announce the entire /14 and both /16 on the ASBR routers using the network command under BGP but an static route pointing to NULL should be use to advertise this prefixes due to BGP does not announce subnets if they are not in the routing table.

[michael.mastropaolo]

Got it.  Ok, so my last question would be, would WAN2 (ASN 64001) then route back into WAN1 (ASN 64002) in the same manner; that is to say, based on location it will choose the closest path?  I guess the core routers in WAN2 would have to advertise a higher local pref to THEIR peer routers in the distribution layer for this to happen correct?  So it's basically mirrored from what we discussed above.  

Am I missing anything else? 

This is awesome all, thank you very much.

[Deivid85_ · Accepted solution]

If you are in charge of managing the AS64001, you can use LOC_PREF inside the AS, as you have said, to choose through which ASBR the AS64002 is reached. If not, other BGP mechanisms can be used to announce to the routers in AS64001 the best path to AS64002, such as MED or AS PATH Prepend. Note that LOC_PREF is used only inside the AS (It is not set on eBGP updates).

[michael.mastropaolo]

Great, thank you.  I shall give this a go.  Much appreciated.