Knowing your IP subnet mask allows you to hide the network portion of your computer identity. It also allows you to create multiple sub-networks from the primary network IP address.
The IP subnet mask works with the IP address to split network traffic into manageable groups. Using these groups alleviates congestion within the network.
A host address and a network address make up an IP address. The subnet mask of the identifies to which part of the IP address a subnet belongs.
Click on the 'Start' button, then click on "Run." Type "cmd" into the "Run" box and press "Enter." A command prompt will open. Type "IPCONFIG" into the command prompt. Your subnet mask will display next to "subnet mask" in the list.