Open a terminal window to get to the command line.
Issue the command ipconfig and press Return. On Linux type ifconfig instead.
Note your own IP address and the subnet mask.
If the subnet mask is 255.255.255.0 the first three sections in your own IP address applies to the entire subnet
Use the command for /l %i in (1,1,254) do @ping X.Y.Z.%i -w 10 -n 1 | find "Reply" where X.Y.Z is the first part of your own IP address