The network is a hub and spoke wherein there are 2 spokes and the spokes have an ISDN backup link between them.
The MPLS provider offers the Peer VPN Model (PE-based), with the peering taking place with eBGP. My understanding of the Peer VPN is that the CE forms an adjacency (eBGP in this case) with it's directly connected PE and does NOT have any adjacencies to the other CE's.
The IGP on the CE's is currently OSPF with all 3 sites in Area 0 (currently configured as p-2-mp over frame-relay. When the MPLS is implemented, each site will be an independent OSPF Area 0 (correct me if wrong).
ISDN is in place between the 2 spokes so they can communicate if the hub site fails.
When moving to the new DCLI's the IP addresses of the p-2-mp OSPF links will go away, so there is no problem there with IP Address overlap.
The problem is with the ISDN links - there will be 2 distinct VPNs to 2 different locations where the same network will be configured. As far as I know, even with route distinguishers, it won't work. When the ISDN is quiet, it's not so much a problem, but when both the frame and the ISDN are up (backup load threshold on frame reaches 75%, etc) is it a problem then?
I think the answer is to use a route-map and not distribute that network to BGP.
Any alternative designs, configurations, or best practices are appreciated. Thank you!
