cidrcalc

CLI for calculating the biggest CIDR from a list of IPs.

Install:

go install github.com/maelvls/cidrcalc@latest

Examples:

$ dig +short clouddocsdev.s3-website-us-west-2.amazonaws.com | grep -Eo '([0-9]{1,3}\.){3}[0-9]{1,3}' | cidrcalc
Largest CIDR block: 52.0.0.0/8

Alternatively, use -hostname flag to resolve the IPs from a hostname without having to use dig:

$ cidrcalc -hostname clouddocsdev.s3-website-us-west-2.amazonaws.com
Resolved IPs for clouddocsdev.s3-website-us-west-2.amazonaws.com: [52.218.153.66 52.218.252.146 52.92.225.227 52.218.188.3 52.92.206.163 52.92.204.171 52.92.213.51 52.92.209.3]
Largest CIDR block: 52.0.0.0/8