Abstract: Open Shortest Path First routing protocol or simply OSPF routing protocol is an Internal Gateway Protocol (IGP) used to exchange routing information within an Autonomous System (AS). OSPF follows Link-state routing protocol rather than the distance-vector protocol. In Link-state routing protocol, each router describes itself and its interfaces to its directly connected objects unlike distance-vector routing protocol which sends its neighbour a list of all known networks along with its own distance to each one of these networks. It uses LSAs to advertise the distance to directly connected links. It is a classless protocol and supports VLSM (Variable Length Subnet Masking). It uses the concept of areas to implement hierarchical routing and area 0 is considered as the backbone area and area n, where n=1, 2, 3,.. is connected to the backbone area using virtual links. In this paper OSPF routing protocol is being configured in an AS and routing is carried out using LSAs. OSPF is preferred over other routing protocols because in OSPF only the new or updated values are transferred instead of sending the entire code and has fast convergence. We use network simulator 3 to build the situation and solve the problem. In this paper we also illustrate the setting of CTY, TTY, AUX and VTY password, create interface loopbacks to test the advertisement by OSPF routing protocol configured on each router and other aspects of OSPF routing protocol with great fervour.
Keywords: Open Shortest Path First routing protocol, Autonomous System (AS), CTY, TTY, AUX and VTY password, fast convergence, hierarchical routing, VLSM (Variable Length Subnet Masking), route summarization, interface loopbacks.