[CentOS] ip range cidr calculator

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?

-- 
MELVILLE THEATRE ~ Melville Sask ~ http://www.melvilletheatre.com