Router(config)# router eigrp 100"No auto-summary" command is needed because by default EIGRP will behave like a classfull routing protocol which means it won’t advertise the subnet mask along the routing information. For example 22.214.171.124/24 and 126.96.36.199/24 will be advertised as 188.8.131.52/8 and 184.108.40.206/8. Disabling auto-summary will ensure EIGRP sends the subnet mask along
Router(config-router)# no auto-summary
Summaries can also be produced manually on any interface
Router(config)# interface < interface >Example:
Router(config-if)# ip summary-address eigrp < as-no> <summarized_network_ip> <summarized_subnet_mask>
Router(config)# interface fa 0/0The manually-created summary route is not advertised as an internal EIGRP route, but instead is classified as an EIGRP summary route. An EIGRP summary route has an Administrative Distance of 5.
Router(config-if)# ip summary-address eigrp 100 220.127.116.11 255.0.0.0