Open Shortest Path First version 2 (OSPFv2) is a routing protocol described in RFC2328. It is a Link State-based IGP (Interior Gateway Protocol) routing protocol applied to routers grouped into OSPF areas identified by the routing configuration on each routing switch. It is widely used in medium to large-sized enterprise networks.

The characteristics of OSPFv2 are:
  • Provides a loop-free topology using SPF algorithm.

  • Allows hierarchical routing using area 0 (backbone area) as the top of the hierarchy.

  • Supports load balancing with equal cost routes for the same destination.

  • OSPFv2 is a classless protocol and allows for a hierarchical design with VLSM (Variable Length Subnet Masking) and route summarization.

  • Provides authentication of routing messages.

  • Scales easily using the concept of OSPF areas.

  • Provides fast convergence with triggered, incremental updates via LSAs.

Some OSPFv2 configuration is done in the global configuration context, others in the router ospf context, or in the interface configuration context, or in the vlink context. OSPFv2 can be configured on L3 ports, VLAN interfaces, LAG interfaces, and loopback interfaces. All such configurations work in the mentioned interfaces context. OSPFv2 mandates the associated interface to be a routed interface.

Supported features

  • OSPFv2 neighbor adjacency, Hello protocol, multiple areas, Inter-area routing
  • AS external routes, stub areas, totally stubby areas, NSSA, ABR, ASBR
  • Designated Router/Backup Designated Router
  • Point-to-point interfaces/broadcast interfaces
  • Virtual Links
  • Bidirectional Forwarding Detection (BFD) - refer to the High Availability Guide for additional information

  • Equal-cost multipath
  • Null authentication, Simple password authentication, MD5 authentication
  • Area range aggregation - Type-3/Type-7 Address Ranges
  • Graceful Restart - un-planned, restart interval, Graceful Restart Helper
  • Stub router advertisement
  • Configuration of interface parameters such as priority, cost, hello-interval, dead-interval, retransmit-interval, transit-delay, etc.
  • Configuration of virtual link parameters such as hello-interval, dead-interval, retransmit-interval, transit-delay, etc.
  • Route redistribution
  • Passive interfaces
  • Multi VRF support with each VRF having one OSPF process instance
  • Congestion control (prioritizing hello packets, inactivity timer reset, and adjacency throttling)