The network command

This is a simple logic that was simple to understand but it took me almost 5 days to understand.

The network command in EIGRP is very brain chewing command for me.

I wanted to understand how it works exactly. Below is my explaination.

Above is my network diagram.

Below are the commands the I used on R1

# router eigrp 1

# network 192.168.1.0------>A

# network .............. ------->B

A> By default the eigrp auto summarizes to classful network. Hence it will always be 192.168.1.0/24 in the routing table.

B>

Case I> Check all WC carefully

network 10.0.0.0

or

network 10.10.0.0 0.0.255.255

or

network 10.10.1.1 0.0.0.0

or

network 10.10.0.0 0.0.3.255

will all give same result i.e. in the routing table of R0 you will always find 10.0.0.0/8

since it will automatically summarize to classful subnet

With no auto-summary you are disabling the auto summarization to classful subnets

Case II> This is most interesting

I have one more network in the R1 side 10.10.222.0/24 network

a> network 10.0.0.0 or network 10.10.0.0 0.0.255.255 will allow us to ping 10.10.1.1 from R1

b> if I use

#network 10.10.0.0 0.0.3.255

#no auto-summary

then this command will exclude the 10.10.222.0 subnet from my network command and pinging it will not be possible from R1.

============================================

Conclusion :

a> network command helps to determine what networks are eligible to be advertised

b> better always use no auto-summary

c> then sends advertisement on 224.0.0.10

Need expert comments on this