Summary route for EIGRP

hi,

I want to summarize the following networks for eigrp but think i maybe making a mess of it:

C 50.0.0.0/16 is directly connected, Loopback50
C 50.1.0.0/16 is directly connected, Loopback51
C 50.2.0.0/16 is directly connected, Loopback52
C 50.3.0.0/16 is directly connected, Loopback53
C 50.4.0.0/16 is directly connected, Loopback54
C 50.5.0.0/16 is directly connected, Loopback55
C 50.6.0.0/16 is directly connected, Loopback56
C 50.7.0.0/16 is directly connected, Loopback57

so far I have worked out that the wildcard mask would be 0.7.255.255 and then I subtract 255.255.255.255 to give me 255.248.0.0. I then goto the interfaces its on and would need to type ip summary address eigrp 75 50.0.0.0 255.248.0.0
but i dont know if the actual summary is right?
can anyone tell me if what I have is right or wrong and how i can get it right please?

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Comments

advanex1

You're right.

Break it down into binary, it's much easier to look at it.

50.0 00110010 00000000
50.1 00110010 00000001
50.2 00110010 00000010
50.3 00110010 00000011
50.4 00110010 00000100
50.5 00110010 00000101
50.6 00110010 00000110
50.7 00110010 00000111

What bits do every network have in common? It would be all of the first octet and the first 5 bits of the second octet. If you treat those as if they were "turned on" ,11111111 11111000, you would get a subnet mask of 255.248.0.0 which would be a route summary of 50.0.0.0 - 50.7.255.255.

So in summary, just go from left to right, identify the common bits and the common bits make up your subnet mask. Hope this helps.

MrXpert

Hi Advanex1, thank you so much for your help! your explanation really helped clear up my doubts