Auto-summary behaviour with EIGRP
I understand the EIGRP auto-summary feature summarizes a subnet
to it’s classsfull network when crossing a classfull network boundary. However,
I am seeing different results when using the network command to advertise the subnet vs. redistributing it via connected.
For example, see below. I have two routers R2 (auto-summary) and R3 (no auto-summary) connected together running EIGRP 60 between them using the 220.127.116.11/24 subnet. R2 also has a directly connected LAN segment 192.168.0.16/29.
192.168.0.18/29 – R2 - 18.104.22.168 <---EIGRP 60 ----> 22.214.171.124 - R3
When I advertise the 192.168.0.16/29 subnet on R2 via the 'network' command, the subnet appears in R3's routing table as 192.168.0.0/24.. which is expected. However, if I advertise the 192.168.0.16/29 subnet with the 'redistribute connected' command, the subnet appears in R3's routing table as 192.168.0.16/29 and no auto-summarization has occured.
I tested exactly the same scenario as above using RIPv2 instead of EIGRP, and auto-summary is in effect when using either the 'network' command, or redistributing the subnet on R2.
Can anyone explain this behaviour? EIGRP appears to handle the auto-summary command slightly differently than RIPv2 when it concerns redistribution.
Thanks for your help.