Open Shortest Path First (OSPF) is a dynamic routing protocol for use in Internet Protocol (IP) networks. OSPF is designated by the Internet Engineering Task Force (IETF). Specifically, it is a link-state routing protocol and falls into the group of interior gateway protocols, operating within an autonomous system (AS). Unlimited router can be used. CPU usage will be high, to reduce the CPU Usage using area.
What are the areas in OSPF?
• The backbone area, which is also referred to as Area 0. All other areas must connect to the backbone area. Hence, this area is obligatory.
• An ordinary or standard area, which is an area that connects to the backbone (Area 0) and is treated as a separate entity. All routers in a standard area have the same topological database, but their routing tables will be based on the routers position in the standard area and will thus be unique to the router.
• A stub area, which is an area that does not accept external summary routes. A router within a stub area can only see outside the autonomous system if a default route has been configuration for it.
• A totally stubby area, which is similar to a stub area. In this area, the default route must be configured as 0.0.0.0. This type of area is useful for remote sites that have few networks and limited connectivity with the rest of the network and is a Cisco proprietary solution.
• A not so stubby area (NSSA), which is a stub area that can receive external routes but will not propagate those external routes into the backbone area.
What are the network types in OSPF?
1.Non broadcast - This is the default on frame relay networks has a DR/BDR election. Neighbor command needed to establish adjacency.
2. Broadcast - This is the default on Ethernet/broadcast networks. Does have DR/BDR election.
3. Point-to-point - No DR/BDR election. This one is pretty self explanatory.
4. Point-to-multipoint - Does not have a DR/BDR election. Solves some design issues with the next hop processing for NONBROADCAST. Treats as a collection of P2P links.
5. Point-to-multipoint non broadcast - Same as P2M but does not use pseudo broadcast. Must statically define neighbors.
6. Loopback - OSPF treats these as stub hosts. (/32)