If you need to find a username of a device with an associated IP address on Active Directory then you can use the following method to find out the username:
At the command prompt enter the following command:
C:/>nbtstat –a ipaddress
Where IP address is the ip address of the device name you are searching for,.
This will list the machine name using that IP address.
Then run the following command:
C:/>net view /domain:ad > anyfile.txt
Where AD is the name of the domain you want to search and anyfile.txt is the name of the file to contain the output.
This will generate a list of every machine and who is logged in.
Open the output file and search for the machine name determined in step 1 (the username will be listed next to this).