Network Warrior, 2nd Edition

Mutual Redistribution

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 50.50.50.0 to route to a host on the 70.70.70.0 network, EIGRP routes will need to be redistributed into OSPF. Conversely, if hosts on the 70.70.70.0 network wish to talk with the hosts on 50.50.50.0, 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 20.20.20.0 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 ...