EIGRP and early IGRP are released by Cisco. They’re both distance vector protocols. EIGRP is enhanced edition of Interior Gateway Routing Protocol. Though it adopts distance vector algorithm, it has some features of link state protocol. EIGRP has improved a lot compared to IGRP; it relies on the Diffused Update Algorithm (DUAL) to calculate the shortest path a destination within a network. It is totally loop-free, and has very fast convergence speed among all the routing protocols. EIGRP is an enhanced distance vector protocol, relying on the Diffused Update Algorithm (DUAL) to calculate the shortest path to a destination within a network. The strengths of EIGRP are Fast convergence EIGRP is an advance distance vector protocol, one of its core strengths is its fast network convergence capabilities, unlike other routing protocols EIGRP keeps feasible successor routes right into the routing table, and this allows millisecond convergence should the successor route fail. Flexible in summarization Unlike OSPF, EIGRP allows you to summarize anywhere, in bigger environments where routers are advertising hundreds of networks, route summarization can greatly enhance router's and network operational capabilities, its less taxing on CPU/memory and cheaper to run / maintain. Unequal cost load- balancing EIGRP allows unequal cost load balancing, which means you can use 2 different cost links to load balance traffic, no other protocol can do this. It is VLSM friendly unlike other distance vector protocols, and EIGRP supports VLSM and discontinued networks. EIGRP is also less confusing than OSPF because it does not have different network types and EIGRP is easier to deploy in hub and spoke scenarios. EIGRP uses a flat network without areas, this can both be an advantage and disadvantage. OSPF is obviously an open standard so it's the logical choice if you have multiple vendors. It can perform well but it requires that you tweak SPF timers because by default in IOS there is a 5 second wait before running the SPF algorithm. OSPF uses areas which means you can segment the network more logically. OSPF can only summarize between areas. OSPF is link state so it has a better view of the entire network than EIGRP before it runs the SPF algorithm. Network administrators will usually be more comfortable with OSPF because it's more commonly deployed.