Hey, i came across this website after strolling around the web aimlessly. It’s IP Subnet Calculator written in perl. Great tools if you are lazy enough to calculate the subnet by your own. The web application is downloadable and in perl. And of course You can host it on your website for other people to use and benefit too.
This applications works great if you want to design your network and break it into a more manageable subnet.
Here’s the link : Perl Ipcalc
I hope that some people would develop an ip/subnet calculator for IPV6 and release it under one of the FOSS license. I’m too busy (and sometime too lazy?) to write one…
p/s : freeware would be ok, but FOSS is way-way better, because other people could port it on other platform.