A. There are numerous downloadable and Web-enabled tools to choose from. However, I recommend this calculator (in particular, the classless version). (See this figure.) This calculator is simple to use and lets you enter an IP address, required subnet mask, or just the number of bits to use. It then displays the network and the address ranges to use for clients. Alternatively, you can tell the calculator how many networks or host addresses you need, and it will set the subnet mask accordingly.