routing summary in eigrp

[engamb1991]

what are the difference between command

1) auto-summary 

2) for ex :  ip summary address eigrp 1 90.0.0.0 255.255.0.0 

[sumit menaria]

EIGRP auto summarization applies to the entire EIGRP process. The ip summary-address command let's you manually summarize that network only out of the applied interface. You could have a network out that interface that could be summarized but other routes in other places that can't be summarized.

So if you have some networks like 10.0.0.0/24 10.0.1.0/24 10.0.2.0/24 10.0.3.0/24,then auto-summary will advertise 10.0.0.0/8 to the neighbors ,,however io summary address eigrp 10.0.0.0 255.255.252.0 will summarize the 4 prefixes into one.and the EIGRP neighbor will have 10.0.0.0/22 in its topology table.

Hope it helps.

[engamb1991]

thanks for your help :)

so the auto-summary for classful and the ip summary used for vlsm is that right 

[sumit menaria · Accepted solution]

We could consider auto-summary for classful but IP Summary for summarizing prefixes going out of an interface to the nearest supernet (VLSM)

Cheers!

Sumit