EIGRP Automatic Summarization

[rhamdaoui1]

Im having an issue with eigrp automatic summarization, we have an eigrp neighbprship on 10.1.100.0/24 and we're trying to advertise a loopback 10.1.3.1/30 on a router (on which automatic summarization is enabled),but when we verify the routing table in the other side the loopback is received with /30.

is it the normal behavior when trying to summarize an address in the same classful network of one of the physical addresses of the router interfaces ?

[willwetherman]

Hi,

Yes this is normal and expected behaviour.

Automatic address summarisation only occurs when an update crosses a major network boundary. In your example, the IP network between your routers 10.1.100.0/24 and the loopback IP address 10.1.3.1/30 both fall within the same classful network 10.0.0.0/8 so automatic summarisation will not occur. However, if you configure the loopback interface with IP address 172.16.1.1/30 then this will be automatically summarised as 172.16.0.0/16 between routers as 172.16.1.1/30 and 10.1.100.0/24 are in different classful networks.

Hope this helps

[rhamdaoui1]

Thank you very much that was very helpful