Dell N3200-ON Networking N-Series Switches User Guide version 6.8.0 - Page 1217

What Are OSPF Routers and LSAs? When a Dell Networking N-Series switch is configured to use OSPF for dynamic routing, it is considered to be an OSPF router. OSPF routers keep track of the state of the various links they send data to. Routers exchange OSPF link state advertisements (LSAs) with other routers. External LSAs provide information on static routes or routes learned from other routing protocols. OSPF defines various router types: • Backbone routers have an interface in Area 0. • Area border routers (ABRs) have interfaces in multiple areas. • Internal routers have all their interfaces in a single OSPF area. • Autonomous system boundary routers (ASBRs) redistribute routes from other protocols and originate external LSAs. How Are Routes Selected? OSPF determines the best route using the route metric and the type of the OSPF route. The following order is used for choosing a route if more than one type of route exists: 1 Intra-area (the destination prefix is in the same area as the router computing the route) 2 Inter-area (the destination is not in the same area as the router computing the route 3 External Type 1 (Preferred) 4 External Type 2 (Default) How Are OSPF and OSPFv3 Different? OSPFv3 is the Open Shortest Path First routing protocol for IPv6. It is similar to OSPFv2 in its concept of a link state database, intra/inter area, and AS external routes and virtual links. It differs from its IPv4 counterpart in a number of respects. Peering is done through link-local addresses, the protocol is link rather than network centric, and addressing semantics have been moved to leaf LSAs. OSPF and OSPFv3 1217