Novice networker here.
I can't seem to find any straightforward answers online.
Example:
IP SUBNET NEXT HOP
> 129.10.112.0 255.255.255.0 R1
> 129.10.80.0 255.255.255.0 R1
> 129.10.0.0 255.255.0.0 R2
> 129.10.63.0 255.255.255.0 R4
> 129.10.63.0 255.255.255.0 R4
> 129.10.64.0 255.255.192.0 R3
> 129.10.65.0 255.255.255.0 R4
> 129.10.66.0 255.255.255.0 R4
What is the proper method to aggregate these entries into the minimum number of entries?
Best Answer
First, separate the entries by next hop. You have to summarize them separately:
Then for each next next hop, convert all the network addresses to binary. Here is just the first one:
Now find all the identical digits, starting from the left. In this case, the digits are all the same up to the 18th position. So your new mask is /18. Now, using either address and the /18 mask, find the network address by ANDing the address and the mask:
So the best summarization of the first two routes is 129.10.64.0/18.
(the rest is left as a exercise for the reader)