Cisco IOS Cookbook, 2nd Edition

EIGRP Stub Routing

Problem

You want to stabilize your network by sending smaller routing tables out to stub branches and reducing the scope of EIGRP queries.

Solution

To enable stub routing, use the eigrp stub configuration command:

Router1#configure terminal 
Enter configuration commands, one per line.  End with CNTL/Z.
Router1(config)#router eigrp 55
Router1(config-router)#eigrp stub 
Router1(config-router)#exit
Router1(config)#end
Router1#

Discussion

This feature became available starting in IOS 12.0(15)S. It is most commonly used in hub-and-spoke network designs where a remote router connects to the rest of the network through only one or two central routers, and where the remote router is the only connection for a small number of LAN segments. In general, you would configure the central routers in this case to send only a default route, as discussed in Recipe 7.9.

In situations when a route suddenly goes away, by default, every router will ask all of its neighbors if they have a path to that remote network. However, it is never going to be fruitful to ask these remote branch routers if they can reach the missing network. If these stub routers are reachable at all, they will already be exchanging information about the few networks that they can access. No trick of topology will allow them to find the missing route if the central routers don’t have it. So the EIGRP stub feature disables these queries. This should help to improve overall network stability. And, in particular, this feature ...