What is the subnet mask?
A. As has been shown the IP address consists of 4 octets and is usually displayed in the format 200.200.200.5, however this address on its own does not mean much and a subnet mask is required to show which part of the IP address is the Network ID, and which part the Host ID. Imagine the Network ID as the road name, and Host ID as the house number, so with “54 Grove Street”, 54 would be the Host ID, and Grove Street the Network ID. The subnet mask shows which part of the IP address is the Network ID, and which part is the Host ID. For example, with an address of 200.200.200.5, and a subnet mask of 255.255.255.0, the Network ID is 200.200.200, and the Host ID is 5.