permit 20 set tag 110 The route maps are the same on R2 because the same rules apply, and we need to test for any routes redistributed from other routers. When a route is redistributed from OSPF into EIGRP, it will be assigned a tag of 110. Routes redistributed from EIGRP into OSPF will be assigned a tag of 90. When a route tagged with 90 is seen in OSPF, we'll know it was sourced from EIGRP, because the tag value will have been set to 90. When this route then comes to be redistributed into EIGRP from OSPF on the other router, the route map will deny it. Thus, a route cannot be redistributed into EIGRP if it originated in EIGRP. OSPF-sourced routes are similarly blocked from redistribution back into OSPF. While this design does prevent routing loops, it does not solve the problem of R3's 50.50.50.0/24 network being advertised through the wrong protocol. R2 is now point- ing back to OSPF for this network: R2#sho ip route [text removed] Chapter 11: Redistribution Gateway of last resort is not set 50.0.0.0/24 is subnetted, 1 subnets 50.50.50.0 [110/100] via 10.10.10.1, 00:11:50, FastEtherneto/o 20.0.0.0/24 is subnetted, 1 subnets 20.20.20.0 is directly connected, FastEtherneto/1 10.0.0.0/24 is subnetted, 1 subnets 10.10.10.0 is directly connected, FastEtherneto/o Every network is different, and there will always be challenges to solve. In this case, we might have been better off with the first design, where each router was only redistrib- uting in one direction, even though that design is not very resilient. The way to solve the problem and provide multiple mutual redistribution points is to combine the two scenarios. With route maps, we can match multiple tags, SO in addition to denying any routes already redistributed into EIGRP on R2, we can also match on the 3 tag we set on R3: route-map EIGRP-to-OSPF deny 10 match tag 110 3 route-map EIGRP-to-OSPF permit 20 set tag 90 The line match tag 110 3 means, "Match on tag 110 or 3." Now R2 has the right routes: R2#sho ip route [text removed] Gateway of last resort is no