OSPF (Open Shortest Path First Open Shortest Path First) is an internal Gateway Protocol (Interior Gateway Protocol, IGP), for a single autonomous system (AS) autonomous system, decision-making in routing, is an implementation of link-state routing protocols, belonging to the internal Gateway Protocol (IGP), so the operation within the autonomous system and famous dix algorithm is used to calculate the Shortest Path tree, OSPF support load balancing and routing based on service type, also supports multiple routing form, such AS a specific host route and subnet route,