Open Shortest Path First (OSPF) is a type of routing protocol known as an interior gateway protocol or an interior routing protocol. The routers in an internet are responsible for receiving and forwarding packets through the interconnected set of networks. Each router makes routing decisions based on knowledge of the topology and traffic/delay conditions of the internet. The routing protocol between routers is used to exchange topology and traffic delay information. An interior routing protocol is used within a portion of the internet called an autonomous system, which simply means a connected set of routers that are managed by a single organization. OSPF is the most commonly used interior routing protocol.

Enhanced Interior Gateway Protocol It is a Cisco proprietary protocol. It uses bandwidth and delay by default to calculate the best path. It can also use load and delay, but these are usually not used. It is a distance vector routing protocol. It keeps a topology map, but it is only similar to the topology map of link state routing protocols.

1.) Mesh topology:- Routing protocol such as RIP(routing information protocol) or OSPF (open shortest path protocol) is used.

2.) Star topology:- Ethernet, token ring, Local Talk, ATM........... all are used...

3.)Bus topology:- Ethernet protocol using CS-MA/CD as access method.....

EIGRP

OSPF is short form of open shortest path first. OSPF is based on linked state routing.