EIGRP - Summarization per interface

When configuring EIGRP, it is possible to apply summarization globally or on a per interface basis. The latter allows for more granularity in the configuration of EIGRP and the way in which routes are shared with specific EIGRP neighbors.

This can be configured using the ip summary-address eigrp interface configuration command. For example, the following two commands cause any EIGRP updates sent out of FastEthernet 0/0 to be summarized as indicated:

R1(config)#interface fastEthernet 0/0 R1(config-if)#ip summary-address eigrp 1 R1(config-if)#ip summary-address eigrp 1

If the subnet mask is not indicated, then the classful subnet mask will be used. Multiple summary addresses can be applied to a single interface.