EIGRP vs OSPF: What's the Difference?

Posted on August 1, 2018
July 10, 2020
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EIGRP (Enhanced Interior Gateway Routing Protocol) and OSPF (Open Shortest Path First) are two common routing protocols specifying how routers or data switches communicate with each other. They are often applied in different situations for varied performance on speed, delay, etc. What’s their differences on earth? Get all you want to know through the detailed comparison of EIGRP vs OSPF below.

EIGRP vs OSPF: EIGRP

EIGRP Topology Example

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EIGRP vs OSPF: OSPF

OSPF Topology Example

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EIGRP vs OSPF: What's the Difference?

One of the frequently asked questions on EIGRP and OSPF is “which protocol is better, EIGRP or OSPF?”. To answer this question, you’d better get to know the difference between EIGRP and OSPF, and have a thorough understanding of their pros and cons.

EIGRP vs OSPF: Algorithm

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.

EIGRP vs OSPF: CPU Usage

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 vs OSPF: Convergence Time

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.

EIGRP vs OSPF: Design

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.

Data Center and Cloud Application Area

OSPF is a better choice when your network is hosted in a data center or cloud-based solution. As OSFP is normally running in most DC networks, it could do some fine tuning in the network infrastructure underlying and exchange routing information with the firewall.

Scalability & Service Provider Support

OSPF scales better than EIGRP because EIGRP is more complex in very large scale networks while troubleshooting. Compared to EIGRP, OSPF is better to use on WAN since most of the service providers support it. OSPF have already been running in internal environments as an IGP (Interior Gateway Protocol). Thus, it is easier for an exchange of certain routes with OSFP. If you want to use some other routing protocol and exchange the same routing information, routing will become more complicated since there will be a redistribution between the already built-in OSPF and another protocol.

Unequal Path Load Balancing

EIGRP is the only protocol supporting unequal path load balancing, which helps routers route traffic across links of different bandwidth.

For more details of EIGRP vs OSPF, go through the table below:

Item OSPF EIGRP
Working on a Ring Topology Better than EIGRP Not good
Working on Hub and Spoke Works poorly Works very well
Suitable on WAN Yes Yes
Suitable for Data Center Better than EIGRP Worse than OSPF
Standard Protocol Yes No
MPLS Traffic Engineering Support Yes No
Suitable as Service Provider IGP Yes No
Complexity More complex Easier
Default Convergence Slow convergence with the default timers Fast with feasible Successor

EIGRP vs OSPF: Which One to Choose?

Given all the comparison on EIGRP vs OSPF, you may have a clear understanding of the two routing protocols. Both of them could be widely deployed in Internet Protocol (IP) networks for data communication. EIGRP is a popular choice for routing within small and big campus networks. While, 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).

Related Article: RIP vs OSPF: What Is the Difference?OSPF vs BGP: Which Routing Protocol to Use?