LSP with a fixed metric of one when next-hop is enabled

When you enable next-hop MPLS without an option, BGP uses an LSP with a fixed metric of one to resolve the routes. For routes that cannot be resolved through the MPLS tunnels, the Extreme device uses the routing table to resolve BGP next hops.

The following steps describe the resolution process for each unique BGP next hop.

1. BGP determines when an LSP can be used to resolve the route for each unique BGP next hop. When BGP can resolve the route, it does not check the native IP routing table. For the next hops that cannot be resolved through the LSP tunnels, the Extreme device uses the IP routing table.
2. For each BGP next hop that is resolved by an LSP, then all possible LSPs to the BGP next hop are selected by default.
3. BGP internally sets this next hop's IGP cost to one instead of the true LSP metric to force it to be the preferred hop instead of a hop resolved by the native IP lookup.
4. The IGP cost is compared for each BGP next hop, and the least-value IGP cost for the next hop or hops are used to install them in the routing table.
   

   Note

   When the Extreme device installs a BGP route in the RIB Manager, it uses the BGP MED, not the IGP metric (IGP cost.)