EIGRP and OSPF are two common routing protocols specifying how routers or data switches communicate with each other. Though they both base on routing algorithms to find the best path for data transmission, EIGRP and OSPF are often applied in different situations for varied performance on speed, delay, etc. Here we will introduce what are EIGRP and OSPF in details, and discuss EIGRP vs OSPF: what's the difference?
EIGRP is short for Enhanced Interior Gateway Routing Protocol. It’s a Cisco proprietary routing protocol which evolves from IGRP (Interior Gateway Routing Protocol). Many network engineers believe that EIGRP is the best choice for a routing protocol on private networks because it offers the best balance between speed, scalability and ease of management.
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OSPF, known as Open Shortest Path First, is an open standard protocol. It is virtually available on any modern enterprise network hardware (Gigabit Ethernet switch, router etc.). Though some engineers think OSPF is a bit more complicated to set up and manage than EIGRP, it's relatively easy to run once you get the hang of things such as autonomous system routing domains. OSPF can be applied to any network unless it is very small, old or primarily Cisco.
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One of the frequently asked questions on EIGRP and OSPF is “which protocol is better, EIGRP or OSPF?”. To answer this question, we’d better get to know the difference between EIGRP and OSPF, and have a thorough understanding of their pros and cons.
EIGRP is based on DUAL (Diffusive Update Algorithm) while OSPF uses SPF (Shortest Path First) algorithm. The major difference between these two algorithms lies in how they calculate the shortest routing path. SPF only depends on bandwidth for metric calculation (SPF bases on bandwidth to calculate the cost of a particular link, the shortest path is the one with least total cost), while DUAL uses bandwidth and delay to calculate the composite metric with a complex formula.
OSPF maintains information about all the networks and running routers in its area. Each time there is a change within the area, all routers need to re-sync their database and then run SPF again. This process makes it more CPU intensive. EIGRP, on the other hand, has triggered and incremental updates. Therefore it is more efficient in terms of CPU usage.
EIGRP’s DUAL algorithm maintains loop free alternative path backup path if available. In other words, when a network becomes unreachable from the best path, EIGRP does its local computation to figure out the next alternative path. OSPF, however, involves a small time to install new route and re-route traffic once a failure occurs. So EIGRP can provide shorter convergence time with minimal network traffic.
Design is also a critical aspect to consider when selecting routing protocols. OSPF area planning requires hierarchically thinking from the backbone area to normal areas. Any area’s size should not become too large for the SPF algorithm to process. If does improperly, OSPF network may become too complex to administer and manage. EIGRP does not have any such area planning requirement.
EIGRP and OSPF have both been widely deployed in Internet Protocol (IP) networks for data communication. EIGRP is a popular choice for routing within small and big campus networks. OSPF is the best choice when your network hardware devices come from various vendors. In addition, If you are using MPLS as the WAN technology, OSPF is also a better option as it has MPLS traffic engineering support with CSPF (Constrained Shortest Path First). So EIGRP vs OSPF: which is suitable for your network?Related Article: RIP vs OSPF: What Is the Difference? OSPF vs BGP: Which Routing Protocol to Use?
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