How to Find a Subnet Mask Number

by Andrew Todd ; Updated September 28, 2017

A subnet mask number is used to determine which part of an Internet Protocol (IP) address is used by the host, and which part is used by the network. A subnet mask, like an Internet Protocol address, consists of four groupings of numbers, separated by periods. For instance, a subnet mask will appear as “255.255.255.0.” Find your subnet mask number using the “ipconfig” command in your command prompt.

Open the Start menu.

Click “Run,” type “cmd” and click “OK” (if using Windows XP or earlier). If using Windows Vista or Windows 7, type “cmd” directly into the search box on the Start menu.

Type “ipconfig” in the command prompt, and press “Enter.” Your subnet mask will be displayed below your Internet Protocol address and will be labeled “Subnet Mask.”

About the Author

Andrew Todd has been writing since 2006. He has written for the Consumer Search website and the U.S. Attorney's Office for the Middle District of Florida. Todd has a Bachelor of Science in criminal justice from the University of Central Florida.

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