http://www.cisco.com/en/US/docs/ios/12_2t/12_2t8/feature/guide/ospfshmk. html
Using a Sham-Link to Correct OSPF Backdoor Routing Although OSPF PE-CE connections assume that the only path between two client sites is across the MPLS VPN backbone, backdoor paths between VPN sites (shown in grey in Figure 2) may exist. If these sites belong to the same OSPF area, the path over a backdoor link will always be selected because OSPF prefers intraarea paths to interarea paths. (PE routers advertise OSPF routes learned over the VPN backbone as interarea paths.) For this reason, OSPF backdoor links between VPN sites must be taken into account so that routing is performed based on policy. -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of null zeroroute Sent: Wednesday, January 13, 2010 2:20 PM To: [email protected] Subject: [c-nsp] BGP to OSPF redistribution I'm having a problem trying to figure out a way to get eBGP learned routes (from a layer-3 VPN MPLS WAN provider) into our internal OSPF, so that the routes learned via the provider are preffered over the internally learned OSPF routes. No matter where the BGP-->OSPF redistribution point is, if it's the PE or CE, the routes will still show up (by default) as OSPF external, and will never be prefferred. The provider who's path we prefer will only run BGP. We would like to use OSPF everywhere if possible, for several reasons. WAN provider A is a layer-3 VPN MPLS network, and is the prefferred path. WAN provider B is a layer-2 VPN MPLS network over which we run OSPF. Provider B's network is inferior at times and we use it as a backup. The equipment where the eBGP peering relationsips exist is a mix of 7600, 3800, 2800, 1800, 6500, 3750, 3550. We considered GRE over the providers network however we then wind up with 25+ tunnels at each location, and that just grows as each new site is added, not to mention some potential issues regarding throughput with a GRE tunnel in the path. Is there a way to redistribute BGP into OSPF so that the routes can be anything but OSPF external? I have not found a way to do this yet, and was wondering if it's even possible, or if I'm missing something obvious. Any suggestions appreciated. _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/ _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
