What is Subnetting
As the name implies, subnetting/subnets are networks created from other networks. This is achieved using network masks, which tell the device an IP is assigned to which network it belongs on. To fully understand the concept of network masks, you need a solid understanding of IP addresses and how they work, you can read my article on IP addresses for more information.
Structure of a Network Mask
A network mask is typically represented by a number that looks just like an IP address. The one most people would be familiar with is 255.255.255.0, which is a class C network, the most common home network configuration. A class C network has 255 IP addresses, 1 – 254 of which can be used, while 0 is the Network ID, and 255 is the broadcast address. A broadcast address is simply the address a packet is sent to if it is meant for everyone on the network capable of receiving it.