When a router learns multiple routes to a specific network via multiple routing processes (or routing protocols), it installs the route with the lowest administrative distance in the routing table. Sometimes the router must select a route from among many learned from the same routing process with the same destination. Each routing process calculates its cost differently and the costs may need to be manipulated in order to achieve load balancing.

OSPF performs load balancing automatically in the following way. If OSPF finds that it can reach a destination through more than one interface and each path has the same cost, it installs each path in the routing table. The only restriction on the number of paths to the same destination is controlled by the maximum-paths command. The default maximum paths is 16, and the range is from 1 to 64.