The TCP/IP Guide - IP Subnetting Step #3: Determining The Custom Subnet Mask
5 Free IP Subnet Calculator Software
IP Calculator / IP Subnetting
IP Calculater Web Tools [cmdref.net - Cheat Sheet and Example]
Subnet Mask - Wildcard Mask Calculator Online
Subnet Calculator Download: Find out the network and broadcast address, subnet and wildcard masks, total available hosts, and other details based on the IP address
IPv4 Subnet Calculator Console Version - TerrorFlatRider
Subnet Calculator for IP Addresses and Subnetting ONLINE!
Subnet Mask Calculator
How to Calculate Network Addresses with ipcalc - Linux.com