Hi everybody ,
I'm confused about
IP summary-address eigrp Command when it use on specific interface , when we need to use it and what is the difference between it and between manual summerization for network ex. 172.16.0.0 0.0.3.255
Your understanding of the network command used in EIGRP is not correct. You are assuming that entering
network 10.0.4.0 255.255.252.0
will summarize the advertisement. That is not the case. If you enter that command EIGRP will look for interfaces that match and will advertise the subnets from those interfaces. It will not summarize any entries.
To explain it in a slightly different way: EIGRP uses the network command only to identify what interfaces are to be included in the dynamic routing protocol process. Once EIGRP has included an interface in the routing protocol process it then looks at the subnet configured on the interface and will advertise that subnet to its neighbors.