 connected routes) have been marked with a tag of 3. EIGRP doesn't do anything with this information other than store it. So what does tagging do for you? Just as you can set a tag to apply when redistributing routes into a routing protocol, you can also test for a tag and permit or deny redistributions based on it. Call me a nerd, but that's pretty cool. To check for an incoming route tag, you again must use a route map. This must be done for all routing protocols, including OSPF. Chapter 11: Redistribution Looking back at the example from Figure 11-6, consider that we've now set a tag of 3 for the connected route 50.50.50.0/24 on R3. If we could prevent this route from being advertised into OSPF, that would solve the problem, because then R1 would never learn of the route improperly. On R2, when we redistribute into OSPF, we need to tell the router to call a route map. We're no longer setting the tag with the redistribute command, as we'll set it in the route map. If I'm checking for a tag using a route map, I always set it there, too. It's easier for me to understand things when I do everything in one place. I've also seen problems where setting a tag with the tag keyword and then checking for it with route maps doesn't work very well. Here, I'm telling the router to redistribute EIGRP 100 routes into OSPF 100, assign them a metric of 10, and apply whatever logic is included in the route map No-EIGRP-Tag3: router ospf 100 redistribute eigrp 100 metric 10 subnets route-map No-EIGRP-Tag3 Here's how I've designed the route map: route-map No-EIGRP-Tag3 deny 10 match tag 3 route-map No-EIGRP-Tag3 permit 20 set tag 2 This one's a little more complicated than the last route map, but it's still pretty sim- ple. The first line is a deny entry. It's followed by an instruction that says, "match anything with a tag of 3." The match coming after the deny can be confusing, but the more you play with route maps, the more this will make sense. The next entry doesn't match anything; it permits everything and then sets a tag of