Command
No Auto-Summary
Use
Disables EIGRP’s default behavior to advertise networks at their classful boundary.
Syntax
Router(config-router)#no auto-summary
Example
In this example, we will disable auto-summary in the EIGRP process and observe the difference. First we will enable EIGRP on all routers for all links.
R1(config)#router eigrp 100 R1(config-router)#network 0.0.0.0
Notice the EIGRP routes are currently shown at their classful boundaries.
R1(config)#do show ip route eigrp 1.0.0.0/8 is variably subnetted, 4 subnets, 2 masks D 1.0.0.0/8 is a summary, 00:00:50, Null0 192.168.13.0/24 is variably subnetted, 2 subnets, 2 masks D 192.168.13.0/24 is a summary, 00:00:51, Null0 D 2.0.0.0/8 [90/156160] via 10.1.1.2, 00:00:50, FastEthernet0/0 D 33.0.0.0/8 [90/158720] via 10.1.1.2, 00:00:51, FastEthernet0/0 D 3.0.0.0/8 [90/158720] via 10.1.1.2, 00:00:51, FastEthernet0/0 111.0.0.0/8 is variably subnetted, 2 subnets, 2 masks D 111.0.0.0/8 is a summary, 00:00:50, Null0 10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks D 10.2.2.0/24 [90/30720] via 10.1.1.2, 00:00:51, FastEthernet0/0 D 10.0.0.0/8 is a summary, 00:00:51, Null0 11.0.0.0/8 is variably subnetted, 2 subnets, 2 masks D 11.0.0.0/8 is a summary, 00:00:50, Null0 D 133.133.0.0/16 [90/158720] via 10.1.1.2, 00:00:51, FastEthernet0/0
Now we will type no auto-summary on all routers.
R1(config)#router eigrp 100 R1(config-router)#no auto
After typing the command, we now see the proper network information.
R1(config)#do show ip route eigrp 2.0.0.0/32 is subnetted, 1 subnets D 2.2.2.2 [90/156160] via 10.1.1.2, 00:00:37, FastEthernet0/0 33.0.0.0/32 is subnetted, 1 subnets D 33.33.33.33 [90/158720] via 10.1.1.2, 00:00:37, FastEthernet0/0 3.0.0.0/32 is subnetted, 1 subnets D 3.3.3.3 [90/158720] via 10.1.1.2, 00:00:37, FastEthernet0/0 10.0.0.0/24 is subnetted, 3 subnets D 10.2.2.0 [90/30720] via 10.1.1.2, 00:00:37, FastEthernet0/0 133.133.0.0/32 is subnetted, 1 subnets D 133.133.133.133 [90/158720] via 10.1.1.2, 00:00:37, FastEthernet0/0