I am having issues understanding when to use SoO where. These are the scenarios I can think of where we'd be using BGP as the IGP and would consider the use of some of these more advanced BGP multi-homing features...
Two sites, different ASNs, no backdoor link - no special config needed Two sites, same ASN, no backdoor link - use either allowas-in or as-override to allow the sites to accept routes from each other - if any of the site are multi-homed, use SoO to keep the routes from circling back into the same site via the other PE Two sites, different ASNs, with backdoor (backup-only) link - peer the backdoor CE routers via eBGP and prepend to prefer the MPLS link Two sites, same ASN, with backdoor (backup-only) link - ??? One site, one ASN, multiple MPLS exit points, with intra-site active (non-backup) links - no special config needed, but MPLS cannot be used if the internal site becomes segmented (due to AS_PATH loop prevention) First, are the above designs correct? And second, what is the proper way to setup "Two sites, same ASN, with backdoor (backup-only) link"? I put it into GNS3, and I can't get the traffic to prefer the MPLS backbone instead of the backup (iBGP) link. The PE routers both prefer the eBGP link towards the internal network, and neither will accept the (preferred) iBGP ad from their peer PE router. It works fine going the reverse -- backup link works great, and if the backup link goes down the MPLS core is used. The only way I can figure to get the desired "MPLS primary, backdoor link is backup" behavior is to do some kludge between the CE routers so that they only advertise the routes to each other if the MPLS network is down. Is the only time you want to use BGP SoO when all your sites are on the same AS (forcing allowas-in or as-override), and some are multihomed? Otherwise, won't BGP AS_PATH loop prevention prevent the looping? Very confused, appreciate your input! Keller Giacomarro [email protected] _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com Are you a CCNP or CCIE and looking for a job? Check out www.PlatinumPlacement.com http://onlinestudylist.com/mailman/listinfo/ccie_rs
