tes (90). OSPF only has one administrative distance for all routes (110). This type of problem can cause no end of headaches in a production environment. If you don't have experience using redistribution in complex environments, this is a very easy mistake to make. Symptoms of the problem include routes pointing to places you don't expect. Look carefully at the design, and follow the route back to its source to see where the problem starts. In networks where you're redistributing between different autonomous systems using the same routing protocol, you may see routes flip-flop back and forth between sources. This can be caused by each AS reporting the same metric, in which case the router will update its routing table each time it receives an update. In the present example, one way to resolve the problem is to stop redistributing the connected route and include the interface into EIGRP with the network command. Using this approach, the route becomes an internal route with an AD of 90, which is more desirable than OSPF's AD of 110. Limiting Redistribution When designing complex networks with multiple redistribution points, you must somehow limit redistribution SO that loops are prevented. I'm going to show you my method of choice, which involves tagging routes and filtering with route maps. Route Tags Many routing protocols-for example, EIGRP, OSPF, and RIPv2 (but not RIPv1)- allow you tag routes with values when redistributing them. The route tags are nothing more than numbers within the range of 0-4,294,967,295. (Unfortunately, the tags cannot be alphanumeric.) Route tags do not affect the protocol's actions; the tag is simply a field to which you can assign a value to use elsewhere. To set a route tag when redistributing into OSPF, add the tag tag# keyword to the redistribute command: 2(config-router)# redistribute eigrp 100 metric 10 subnets tag 2 This command will redistribute routes from EIGRP 100 into OSPF. The OSPF met- ric will be 10, and the tag will be 2. To see the tags in OSPF routes, use the show ip 