If we use the default subnet mask with a Class C network address, then we already know that three bytes are used to define the network and only one byte is used to define the hosts on each network.

Here is an example question : Class C, Five Subnets. the book states that always look in the Y column. ofcourse the closest value for 5 subnets is 6.

Devices also have a subnet mask, which defines which part of the IP address belongs to the network and which part belongs to the device.

How to Calculate Subnets With Microsoft Excel. IP addresses on your company network consist of three parts: the network address, the host address and the subnet mask.

Valid subnet address: To figure out the valid subnet address, simply subtract the subnet mask from 256. For example, if you had a Class A mask of 255.240.0.0, the equation would be 256-240=16.