A command line tool that "compresses" a list of IPv4 addresses into a set of IPs and subnets that moderately well describe the original list.
Efficient firewall rules mostly. If you have a list of IPs you need to white or black list and the list if especially long then the list can become difficult to manage.
The following would ipcompress
a list of IPs (each on a new line) grouping by subnets where more than 20% of the subnet's IPs appear in the list.
./ipcompress iplist.txt 20