I found a command-line program that did this once before, used it for a while and then forgot about it until right now and I'll be damned if I can find it again.
A command line IP calculator that takes an address range and give it back in cidr format.
I found an online one that does this here:
http://www.ipaddresslocation.org/subnet-mask-calculator.php
But I would prefer to have the commandline one back again.
Does anyone know what it's called and where it can be found?
I like the one at http://jodies.de/ipcalc-archive/ipcalc-0.41/ipcalc which also gives Cisco wildcard masks as well as all the other useful things.