Created by - Orhan Ergun
In this post, we will compare EIGRP and OSPF. We will look at some of the important aspects when we compare EIGRP vs OSPF. From scalability, standardization, working on different topologies and many aspects will be compared in this most detailed comparison blog post on the Internet. We prepared the above comparison chart for EIGRP vs OSPF comparison. We will look at some of those important Comparison criteria from a design point of view. EIGRP vs OSPF Scalability OSPF supports two layers of Hiearchicy. OSPF Backbone areas and OSPF Non-backbone areas. EIGRP on the other side supports as many as you want. You can summarize EIGRP prefixes at every hop. This capability provides a scale advantage to EIGRP. In EIGRP, we don't need an ABR node for summarization for example. EIGRP vs OSPF in Full Mesh, Ring and Hub and Spoke Topologies The full mesh may require a lot of logical connections, OSPF with Mesh-group feature can scale but it can be a scaling problem for the EIGRP networks. If we think that in real-life networks, EIGRP is usually used in Hub and Spoke topologies most of the time, expecting EIGRP to run on Full-mesh topologies is not so real. When it comes to large-scale Hub and Spoke topologies, OSPF requires a lot of tuning or it scales very poorly. Because Hub to Spoke connections either will be in the Backbone area, in this case, the backbone can get very large, or we may need to make Hub routers as ABR. It may not be possible always. Ring topologies are usually a nightmare for many aspects of every routing protocol. Converge slowly, hard for the capacity planning as well. EIGRP vs OSPF at the Internet Edge Both of these protocols have been designed as Internal IGP. So, scalability, and policy support are not even close to BGP. They are both excellent Interior Gateway Protocols but they are not suitable for the Internet Edge. EIGRP vs OSPF as Service Provider IGP Protocol IGP protocols in the Service Provider networks are used to provide reachability between the edge nodes of the Service Provider. They don't carry customer prefixes over IGP, for the customer prefixes in the Service Provider, BGP is used. The service provider wants to have a vendor-neutral routing protocol. They don't want to be vendor lock-in. This means Cisco's own routing protocol EIGRP is not suitable for their network, as it is not a standard-based protocol. Also, Service Provider provides SLA, service guarantee, Fast Reroute, and many other capabilities today by running Segment Routing, LFA, Remote LFA, TI-LFA, RSVP-TE, and many other technologies in their network. Most of these technologies, if not all, require topology information. EIGRP doesn't carry topology information in the network. Only OSPF and IS-IS, a link-state protocol do. EIGRP vs OSPF Fast Reroute OSPF can support Fast Reroute with LFA, Remote LFA, TI-LFA, and RSVP-TE FRR as with EIGRP. EIGRP can converge faster if there is a Feasible Successor compared to OSPF but both of them can support IP FRR - Fast Reroute as well. EIGRP vs OSPF Standard EIGRP although there is an EIGRP RFC 7868, is an Informational RFC. Thus EIGRP is not an Industry-standard protocol. OSPF is an IETF standard protocol. EIGRP vs OSPF Complexity Both protocols can be considered easy, although there are so many different types of LSAs and OSPF Areas in OSPF since there is so many public and private resource for it, it reduced the complexity of OSPF over years. EIGRP vs OSPF Resource Requirement EIGRP runs Dual Algorithm for path calculation and OSPF runs Dijkstra/SPF algorithm. Compare to SPF, Dual requires much fewer resources on the Routers. EIGRP vs OSPF Extendibility EIGRP is a TLV based protocol, but OSPF fixed header, so when it comes to extendibility, EIGRP is also a clear winner. EIGRP vs. OSPF IPv6 Support Both EIGRP and OSPF support IPv6 of course. OSPF with the OSPFv3, which is a completely new routing protocol and has many differences from OSPFv2, but EIGRP supports IPv6 without requiring a new protocol. EIGRP vs OSPF Default Convergence From the data plane convergence point of view, which is known as Fast Reroute as well, both protocols converge equally fast. But when it comes to default protocol convergence, or in other words, control plane convergence, it is related to the protocol timers. If all the timers are in default for both EIGRP and OSPF, then the question is whether there is a Feasible Successor - FS, in the EIGRP network or not. When there is a Feasible Successor, EIGRP default convergence can be faster than OSPF. Although there can be many other criteria to compare OSPF BGP, for this blog post, I think it is enough to cover the difference between OSPF and EIGRP. If you want to learn more about these protocols, you can take our OSPF and EIGRP courses or you can check many of our free blog posts on this topic.
Published - Tue, 05 Apr 2022