EIGRP auto-summary

R1 <----> R2 <----> R3

R1 config "no auto-summary"

R2 config " auto-summary"

R3 config "auto-summary"

R3#show ip route ei

     1.0.0.0/24 is subnetted, 1 subnets

D       1.1.1.0 [90/435200] via 10.1.23.2, 00:03:41, FastEthernet0/0

D    2.0.0.0/8 [90/409600] via 10.1.23.2, 00:03:52, FastEthernet0/0

     3.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

D       3.0.0.0/8 is a summary, 00:00:44, Null0

     10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks

D       10.1.12.0/24 [90/307200] via 10.1.23.2, 00:03:52, FastEthernet0/0

D       10.0.0.0/8 is a summary, 00:00:44, Null0

=> chi summary nhung routes local router.