1066 OSPF CommandsRoute PreferencesNormally, OSPF select routes in the following order:• Local• Static• Intra-area• Inter-area• External• RIPPowerConnect OSPF allows the administrator to change the preference forselecting intra, inter, and external routes according to the following rules:a External route preferences apply to all ospf external routes like type1,type2, nssa-type1, nssa-type2 equally.b Multiple route types may be configured with equal preference values.c Configuring a route preference of 255 makes the route ineligible to beselected as the best route to its destination. That is, a route type witha preference of 255 shall never be used for forwarding.The RIP preference is not used in IPv6 routing.OSPF Equal Cost Multipath (ECMP)A device running the IP routing protocol OSPF maintains multiple equal-costroutes to all destinations. The multiple routes are of the same type (intra-area, inter-area, type 1 external or type 2 external), cost, and have the sameassociated area. However, each route is defined by a separate advertisingrouter and next hop.With ECMP, a device forwards traffic to a specified destination throughmultiple paths thereby taking advantage of the bandwidth of both links.ECMP routes are configured statically or learned dynamically as follows:• Configured Statically: If an operator configures multiple static routes tothe exact same destination but with different next hops, those routes aretreated as a single route with two next hops.
