How to Check Which Domain Controller a Workstation Connects To
Domain controllers provide a central location for users to authenticate to the network. These servers are a part of a Windows domain and there are usually two controllers on the domain: a primary and a backup. If you want to know which domain controller is authenticating you on the network, the Windows command prompt is used. The domain controller information is saved in a Windows variable called "%logonserver%."
Click the Windows Start button and select "Run." In the text box displayed, enter "cmd" and press the "OK" button. This opens the Windows command prompt.
Enter "echo %logonserver%" into the command prompt and press "Enter." A server is displayed, which is the name of the domain controller the machine used to authenticate.
Enter "echo username %logonserver%" into the command prompt and press "Enter." Replace "username" with your username or another user who uses the machine for domain access. This displays the logon server for that particular user.