548 G8264 Application Guide for ENOS 8.4Selecting Route Paths in BGPBGP selects only one path as the best path. It does not rely on metric attributes todetermine the best path. When the same network is learned via more than one BGPpeer, BGP uses its policy for selecting the best route to that network. The BGPimplementation on the G8264 uses the following criteria to select a path when thesame route is received from multiple peers.1. Local fixed and static routes are preferred over learned routes.2. With iBGP peers, routes with higher local preference values are selected.3. In the case of multiple routes of equal preference, the route with lower AS pathweight is selected.AS path weight = 128 x AS path length (number of autonomous systems traversed).4. In the case of equal weight and routes learned from peers that reside in the sameAS, the lower metric is selected.Note: A route with a metric is preferred over a route without a metric.5. The lower cost to the next hop of routes is selected.6. In the case of equal cost, the eBGP route is preferred over iBGP.7. If all routes have same route type (eBGP or iBGP), the route with the lower routerID is selected.When the path is selected, BGP puts the selected path in its routing table andpropagates the path to its neighbors.Equal Cost Multi-PathBGP can be configured to load balance the traffic over multiple paths if first sixsteps in path selection are identical and the next‐hop of the route differs.Multipath RelaxBGP multipath relax functionality allows load balancing across routes withdifferent autonomous system paths, but equal in length (same as‐path length).With this option disabled, both autonomous system paths and as‐path length mustbe identical for load sharing. This functionality can be enabled using thecommand:RS G8264(config router bgp)# bestpath as path multipath relax
