8 Replies Latest reply: Mar 9, 2011 4:50 PM by Paul Stewart - CCIE Security RSS

    EIGRP and OSPF comparison




      Question may sound weird but just to tease your brain...


           What is the difference between EIGRP topology table and OSPF topology table?







        • 1. Re: EIGRP and OSPF comparison
          Wesley Kirby

          EIGRP only shows successor and feasible successor routes...OSPF shows all routes it knows.

          • 2. Re: EIGRP and OSPF comparison

            Well, technically OSPF does not have a topology table, it is known as the OSPF database.  But as Wesley mentions, the EIGRP topology table list only successor and FS routes, whereas the OSPF database shows all known routes.  You can have EIGRP show all known routes withe keyword "all-links" at the end of the "sh ip eigrp top" command.


            To summarize each protocol, they both have three "tables", which you can view with the appropriate "show" command,



            eigrp neighbor table

            eigrp topology table

            eigrp routing table



            ospf neighbor table

            ospf database

            ospf routing table





            Message was edited by: Brian

            • 3. Re: EIGRP and OSPF comparison

              EiGRP keeps limited information for each prefix / lenght and its associated routes in its Topology Table: ASN, State, Metric, Outgoing interface, metric vectors + MTU ad hop count.

              Sh eigrp topology only shows Successor and Feasible Successor Routes while sh eigrp topo all-links also list those routes that are neither S nor FS.

              Hence the fast convergence process of EIGRP as a "second best backup" or FS is already kept in memory and in case the "best route" or S fails, can imeditely be used.

              The fact that the FS's requirement is that its Reported Distance (from a Neighbor's perspctive) must be lower than the S Feasible Distance (local) garantee that the Feasible Successor offers a loop-free alternative.


              On the other hand, Link-state protocols, like OSPF must keep an indentical database of LSA: all OSPF routers will have the same LSDB (minus the simplification via DR-BDR) and they keep a "topological view" of the entire network in their OSPF databse (with the Advertising router been a directly connected neighbour).

              • 4. Re: EIGRP and OSPF comparison


                I guess this could help you out.... Please get back if you have any doubt on this ....

                Communication typeRip send entire routing update   to all directly connected interfaceEigrp send multicast Hello   Packet to the NeighborsOspf send multicast Hello Packet   to the Neighbors
                UDP 520 port for broadcast
                Interface TypeRip classifies routers as active   and passive interfaceEigrp also classifies routers as   acitve and passive interface/routeOspf does not classify a router   a acitve and passive interface/route
                MulticastRiv2 Multicast Address Multicast Address Multicast Address   (Spoke Router) and (DR & BDR)
                ConceptEigrp concept : Neighbor Table,   Topology Table, Fessible Successor, Route States
                Auto Summeryauto-summery command enable by   default on routerauto-summery command enable by   default on router
                Global ConfigStatic Routeconfig# ip route   null0
                Support For CIDR and VLSMconfig# no ip classless (by   default enable)Eigrp support CIDR, VLSM
                Turn off routingconfig#no router ip(turn off   routing)Config# no router eigrp 101
                Starting CommandConfig#router ripConfig# router eigrp 101Config# router ospf 100
                Router configNetwork InclusionConfig-router#Network area 1
                Neighbor StatementConfig-routerNeighbor area 1
                Area or Domain ConceptConfig-routerNeighbor area 1(put a no. of subnet into area 1)
                Config-routerNeighbor area 1(any   interface into area 1)
                config-router#log-adjecy-changes   detail
                config-router# area 1 (config   normal area)
                config-router# area 1 stub   (config stub area)
                config-router# area 1 stub   no-summery(config Totally stub area)
                config-router# area 1   NSSA(config Not so stuby area)
                config-router# area 1 NSSA   no-summery(config Not so stuby Totally stuby area)
                Routes SummerizationRiv2 Summerize the network as   classfull boundaryEigrp   summerization support classless
                Turn off Auto Summeryconfig-router# no auto-summeryconfig-router# no auto-summeryconfig-router# no auto-summery
                Maximum Path showed by Routing   PorotocolConfig-router# Maximum-paths ?   (default=4,maximum=6)Config-router# Maximum-paths ?   (default=4)
                Support for Static route to be   advertisedconfig-router#redistribute   staticconfig-router#redistribute   staticconfig-router#redistribute   static
                Timerstimer basic 30 180 180   360(Update, Invalid, Hold Down, Flush)config-router#   default-information-originate
                Default Root Generationconfig-router#   default-information-originateconfig-router#   default-information ?(Allowed, in, out)config-router#   default-information-originate always(these 2 command usually used on ASBR)
                Version StatementConfig-if#ip rip send version   1/2
                Config-if#ip rip receive version   1/2
                Interface ConfigBandwidth  Allocationconfig-if#bandwidth X(allow   eigrp to make better matric calculationconfig-if#bandhwidth 128 (kbps)
                Othersconfig-if#ip   bandwidth-percentage 75 100 (Admin Dist=75 & %=100)config-if#ip ospf priority 50   (to become DR & BDR)
                config-if#ip ospf cost 1564
                Authentication modeconfig-if#ip rip authenticaion   mode (text | md5)config-if#ip authentication mode   eigrp 101 md5config-if# ip ospf   massege-digest-key 1 md5 pswd
                Authentication commandconfig-if#ip rip authenticaion   key-chain pswdconfig-if#ip authentication   key-chain eigrp 101 pswd
                config-if#ip summery-address   ip+maskconfig-if#ip ospf hello interval   30
                config-if# ip ospf dead interval   120
                summerization commandconfig-if#ip summery-address summery-address   eigrp 101 75 (Admin Distance=75)Config-router#summery-address ip   mask prefix mask (not-advertise){summery-address}
                • 5. Re: EIGRP and OSPF comparison

                  OSPF and EIGRP both have 3 Tables as Brian said, but the Topology Table in OSPF refers as the OSPF Database. So the difference is that:


                  * OSPF database keeps all known routes. In other words it is a Road Map of the entire network, where all routers within the same OSPF autonomous System must have identical database.


                  In contrast


                  * EIGRP Topology table only keeps the SUCCESSOR and the FEASIBLE SUCCESSOR, the best route and the backup route. In other words the Plan A and Plan B.

                    From the topology table the DUAL is ran to figure out the best route (plan A) and put into the Routing Table.

                  • 6. Re: EIGRP and OSPF comparison

                    Just wanted to point out there can be from one to six EIGRP feasible successors.

                    • 7. Re: EIGRP and OSPF comparison
                      Elvin Arias

                      The first that you have to know is that OSPF is a link-state routing protocol and EIGRP is an advanced distance vector.


                      The main diferences is that EIGRP topology table don't have knowledge about all the routes in a network and the OSPF topology table do. In the EIGRP topology table are just the sucessor and the feasible sucessors routes and in the OSPF topology table are all the routes for every path in the network.

                      • 8. Re: EIGRP and OSPF comparison
                        Paul Stewart  -  CCIE Security

                        "EIGRP only shows successor and feasible successor routes...OSPF shows all routes it knows."


                        Actually the EIGRP Topology table contains everything.  It just hides it by default.  To see everything--"show ip eigrp topology all-links"