OSPF Routing Fundamentals. OSPF stands for Open Shortest Path First. Definition: OSPF is a routing protocol used to determine the best route for delivering the packets within an IP networks. It was published by the IETF to serve as an Interior Gateway Protocol replacing RIP. The OSPF specification is published as Request For Comments (RFC) 1247. Note that OSPF is a link-state routing protocol, whereas RIP and IGRP are distance-vector routing protocols.