Redistribute EIGRP and OSPF
The use of a routing protocol to advertise routes that are learned by some other means, such as by another routing protocol, static routes, or directly connected routes, is called redistribution. While running a single routing protocol throughout your entire IP internetwork is desirable, multi-protocol routing is common for a number of reasons, such as company mergers, multiple departments managed by multiple network administrators, and multi-vendor environments. Running different routing protocols is often part of a network design. In any case, having a multiple protocol environment makes redistribution a necessity.
Differences in routing protocol characteristics, such as metrics, administrative distance, classful and classless capabilities can effect redistribution. Consideration must be given to these differences for redistribution to succeed.
Enhanced Interior Gateway Routing Protocol (EIGRP)
Enhanced Interior Gateway Routing Protocol (EIGRP) is an advanced distance-vector routing protocol that is used on a computer network for automating routing decisions and configuration. The protocol was designed by Cisco Systems as a proprietary protocol, available only on Cisco routers. Partial functionality of EIGRP was converted to an open standard in 2013 and was published with informational status as RFC 7868 in 2016.
EIGRP is used on a router to share routes with other routers within the same autonomous system. Unlike other well known routing protocols, such as RIP, EIGRP only sends incremental updates, reducing the workload on the router and the amount of data that needs to be transmitted.
EIGRP replaced the Interior Gateway Routing Protocol (IGRP) in 1993. One of the major reasons for this was the change to classless IPv4 addresses in the Internet Protocol, which IGRP could not support.
Open Shortest Path First (OSPF)
Open Shortest Path First (OSPF) was designed as an interior gateway protocol, for use in an autonomous system such as a local area network (LAN). It implements Dijkstra’s algorithm, also known as the shortest path first (SPF) algorithm. As a link-state routing protocol it was based on the link-state algorithm developed for the ARPANET in 1980 and the IS-IS routing protocol. OSPF was first standardised in 1989 as RFC 1131, which is now known as OSPF version 1. The development work for OSPF prior to its codification as open standard was undertaken largely by the Digital Equipment Corporation, which developed its own proprietary DECnet protocols.