The term mutual redistribution refers to when a router redistributes between two routing protocols in both directions instead of just one. Often, we redistribute because there is a device or entity we wish to connect with that doesn’t support the routing protocol we have chosen to use. We need to share routes between protocols, but, if you will, the protocols don’t speak the same language.
Figure 11-5 shows a network in which every subnet needs to be reached by every other subnet. The problem here is that the network on the left is using OSPF and the network on the right is using EIGRP. For a host on 18.104.22.168 to route to a host on the 22.214.171.124 network, EIGRP routes will need to be redistributed into OSPF. Conversely, if hosts on the 126.96.36.199 network wish to talk with the hosts on 188.8.131.52, OSPF routes will need to be redistributed into EIGRP. Because there is only one router connecting these two domains together, redistribution must occur in both directions.
Figure 11-5. Mutual redistribution
To accomplish mutual redistribution on one router, simply configure both protocols for redistribution into the other:
router eigrp 100 redistribute ospf 100 network 184.108.40.206 0.0.0.255 default-metric 100000 100 255 1 1500 no auto-summary ! router ospf 100 redistribute eigrp 100 metric 100 subnets network 10.10.10.0 0.0.0.255 area 0 default-metric 10
The configuration ...