Difference Between EIGRP and OSPF

EIGRP vs OSPF

EIGRP and OSPF are routing protocols used to advertise about routes in a network. EIGRP is a cisco proprietary protocol, and OSPF is an open standard industry protocol, which can also be used with non-Cisco devices like Juniper. Protocols are set of rules and regulations, and routing protocols are used with routers to establish a connection between them. EIGRP and OSPF use Hello messages to find about routes and establish neighbors.

EIGRP

EIGRP supports IP, AppleTalks and IPX, and all data link layer protocols, data-link layer is the 2nd layer in the OSI model where error notification, network topology, and flow control are handled. EIGRP’s neighbor is another EIGRP speaking router in a common subnet; it must pass the authentication process, and use the same autonomous system number. Autonomous system is a set of routers and networks managed by groups of routers where they exchange information using a common routing protocol. EIGRP stores data in three tables called neighbor table, topology table, and routing table. Route information is sent once when establishing a new neighbor adjacency, and after that only changes are advertised. EIGRP uses DUAL (Diffusion Update Algorithm) to select the best path in a network. It’s Advertisement Distance is 90. By AD or administrative distance, we show how believable a route can be. When it takes a lower number, the route becomes more believable. EIGRP keeps brief information to save CPU and memory usage, and it avoids loops keeping that basic information about routes. In EIGRP topology, a successor and a feasible successor is selected in order to route packets efficiently and loop freely in a network. Successor router takes a path with no loops and shortest path in a network to reach another subnet. If it fails, the feasible successor handles the network traffic.

OSPF

OSPF is an Internet Protocol that is widely used as an Interior Gateway Protocol. After gathering information from available routers, it constructs a topology map of a network. OSPF communicate using areas, they form neighbor relationship with routers in the same autonomous system first. Every area must be virtually or directly attached to a backbone area, which is numbered as “area 0”. OSPF maintains the routing table, neighbor table and database table. To select the best path it uses Dijkstra’s Shortest Path First (SPF) algorithm. OSPF selects a DR (Designated Router) and BDR (Border Designated Router) for a network, which can simply be defined as a captain and a vice–captain of a network. Every router is connected to these two main routers and communicates only with them, not with each other. When the DR goes down, BDR takes its place, and takes control of giving orders to other routers. This routing protocol use Advertisement Distance of 110, when advertising its networks.

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