Open Shortest Path First dynamic routing protocol. OSPF is a link state protocol rather than a distance vector protocol. OSPF tests the status of its link to each of its neighbors and sends the acquired information to them.

OSPF, defined by RFC 1257, stabilizes after a route or link failure faster than a distance vector protocol based system. OSPF uses IP directly, not relying on TCP or UDP. OSPF can:

  • Have routes based on IP type of service (part of IP header message) such as FTP or Telnet.
  • Support subnets.
  • Assign cost to each interface based on reliability, round trip time, etc.
  • Distribute traffic evenly over equal cost routes.
  • Uses multicasting.

Costs for specific hops can be set by administrators. Adjacent routers swap information instead of broadcasting to all routers.