IP Addressing Fundamentals

Forming Subnets from 24-Bit Network Addresses

Having explored the basics of subnetting, you are ready for a more in-depth examination of how they are formed and the mathematics on which they are founded. Starting with a 24-bit network address (equivalent to a Class C network), the formation of subnets is limited to between 2- and 6-bit masks. The limited size of masks in a 24-bit network makes for an ideal case study to demonstrate the potential for confusion as to where a subnet begins and ends and why some addresses look valid but aren't.

Let's start by examining the basic trade-off proposition that exists between the number of subnets that can be formed with any given mask size and the subsequent number of usable hosts per subnet. This information ...