ant subnets to be redistributed. Redistributing into OSPF If you do not include the subnets keyword on modern versions of IOS, you will be warned about your probable mistake: R3 (config-router) #redistribute eigrp 100 metric 100 % Only classful networks will be redistributed Mutual Redistribution The term mutual redistribution refers to when a router redistributes between two rout- ing 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. OSPF 100 Area 0 EIGRP 100 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 Chapter 11: Redistribution 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 is simple. I've followed the steps outlined in the preceding sections by establishing a default metric in each protocol, then redistributed accordingly. Noth- ing more needs to be done when there is only one router doing mutual redistribution. Redistribution Loops Things can get interesting when multiple rout