[c-nsp] BGP <-> OSPF default route failover

[tkacprzynski at SpencerStuart.com]

I am trying to figure out what would be the best way to provide redundant Internet access across two sites running BGP full routing tables at the edge and OSPF between the sites. My main goal is to be able to have fail-over to the other site's Internet access in case the Internet circuit goes down. 

Since I won't be getting a default route from the ISP I can't redistribute that default route to OSPF. One way is to just originate a default route from the OSPF process running on the edge provider, but my question is how to take it away if the Internet circuit fails and reroute it to the other site. 

Topology:
(ISP1 ) - Site A (BGP-OSPF)– OSPF Backbone - Site B (OSPF-BGP) - (ISP 2)

If the connection to ISP1 fails, how to I reroute uses from Site A to use Site B's Internet access?

I looked at using “default-information originate always route-map DEPENDENT-ROUTE”  where my dependent-routes would be something like a RR route from the ISP or the ip address of the interface connected to the ISP.3

What do you think is the best way to accomplish this?

Is there anything within iBGP I should look at?


Thank you.