5 Replies Latest reply: Nov 12, 2010 12:56 PM by ciscoboy247 RSS

    Differences between EIGRP and OSPF


      Hello All,


      I want to know the main differences between EIGRP and OSPF features. Why we need to configure OSPF and why not EIGRP at the same place. Major focus on what benefits we can have with OSFP or EIGRP in comparision of both.

        • 1. Re: Differences between EIGRP and OSPF
          Keith Barker - CCIE RS/Security, CISSP

          Hello Ali-


          Main differences:



          Distance Vector but likes to have neighbors similar to link state.

          Supports proportional load balancing.




          Link State

          OSPF can carry additional information for an ISP who is doing MPLS Traffic engineering

          Open standard


          If we run OSPF and EIGRP together, may the protocol that has the longest routes win.     Runner up will be the Administrative Distances.  EIGRP has different ADs for routes, depending on whether they are internal or external, while OSPF stays at 110 for AD.   Both may be changed via configuration.


          There isn't a great need to run both protocols at the same time, or even in the same network, if all devices and services support 1 or the other.


          Best wishes,



          • 2. Re: Differences between EIGRP and OSPF
            Diwakar Sharma -CCNA/CCNP/JNCIA-ER

            EIGRP is and Advanced distance vector routing protocol which uses DUAL (Diffuse Update Algorithm). Distance vertor protocols are also called  as routing by rumour protocols As they are not entirely aware of  topological information.


            Administrative distance (Trustworthiness) : 90 (The lower the better)


            Cisco Routers CPU utiliztion will be less if we use this protocol 


            Limitation : Its proprietary to Cisco Systems  cant be used in Testing environments where you use Avaya and Juniper Routers to check interoperatibility



            OSPF : Dijkstra's algortihm . Link State Protocol.Can be Divided into areas (which is good like stub, Not so stubby, completly stubby.Backbone)


            Opensource: used with Avaya and Juno-OS as well


            This algo (Dijkstra) will run every time in case their is a change in topology and the CPU utilization or the overhead on router is more

            • 3. Re: Differences between EIGRP and OSPF

              Hi Ali


              OSPF has areas and virtual-link so you can partition up your route tables. It will also talk to Computers such as IBM Mainframes.


              Eigrp is simple. Simple to use and requires no thought.


              Regards Conwyn

              • 4. Re: Differences between EIGRP and OSPF

                Hi Ali


                EIGRP also works with unnumbered interfaces.


                Regards Conwyn

                • 5. Re: Differences between EIGRP and OSPF

                  Hi Ali,


                  Here is some of my feedback to your question, based on what I have learned and understood so far.  I have passed my ICND1 (CCENT) and ICND2 (CCNA) and I am busy with my CCNP route studies:


                  In the event of a network failure EIGRP remembers available backup routes and fails over almost immediately, where as OSPF needs to re-run the SPF algorithm to find any "backup" routes which results in extra processor cycles.


                  EIGRP cuts out processor cycles by learning only the best routes from its neighbors (routing by rumor) and because of this it does not have an entire view of all the paths to all the networks, it rather has a view of the network based on its neighbors view.  OSPF neighbors send all info to the DR and BDR which then update all of the other neighbors in the area.  This results in all OSFP routers in the area knowing about all the paths to all the networks at the same time and all routers in the area have the exact same view of the entire network.


                  With OSPF you would need to limit each area to 500 Routers (I think…please check that figure) due to the overhead of the SPF algorithm.  I don’t think EIGRP suffers from a limitation to the amount of routers you can place…this one I am not 100% about (Perhaps one of the CCIE’s could comment on this point).



                  EIGRP is Cisco proprietary where as OSPF is industry standard and plays nicely with other vendor routers.


                  In EIGRP you can summarize networks on any EIGRP router in the network however with OSPF you can only perform summarization on the ABR and ASBR routers.


                  EIGRP supports un-equal load balancing where as OSPF does not.


                  EIGRP (Distance vector) like RIP has the ability to turn off the auto-summary feature which advertizes networks at their classfull boundary by default.  OSPF does not advertize networks at their classfull boundary, nor does it have the ability to turn this feature on.