Here are the following features of the Open Shortest Path First interior gateway routing protocol:
- It is a link-state routing protocol. Review the differences between Link-State and Distance Vector:
- It is defined by the IETF Open Standard RFC 2328. It is not proprietary like EIGRP. (OSPFv2 is used for IPv4, and OSPFv3 is used for IPv6.)
- Is highly scalable and converges quickly
- Uses Protocol No. 89. It does not rely upon TCP or UDP.
- Provides efficient use of updates. All neighbors in an area exchange full database (link-state) information when relationships are built. (All routers maintain a copy of this information.) Once converged, it uses keepalives to maintain adjacencies and does not send routing updates unless there are changes in the topology. When changes occur, only specific updates are propagated to the routers in the area.
- Unicast and multicast support. The protocol does not use broadcast. It uses multicast address 224.0.0.5 for all OSPF routers and 224.0.0.6 for DR and BDR routers.
- Supports VLSM. It carries subnet information, including information about discontiguous networks, in routing updates.
- Supports manual route summarization. You can summarize inter-area routes or external routes at the ASBR. It does not support auto-summarization.
- Supports authentication. Includes clear text, MD5, and SHA.
Stuck-in-Active: Journal of an IT-Network Administrator 