If you are using a Windows computer connected to domain environment, and you need to locate the Active Directory (AD) Domain Controller serving as Logon Server. Bellow is what you should do to find this out.
1. Log into your Computer.
2. Open a command prompt (Start > Run > cmd) or (Windows Key + R).
3. Type echo %LOGONSERVER%
4. This will show up the DC servicing your client computer as credential logon server