Lets say you have more than one domain controler in your organization. If your having issues with services not logging for some reason, you may want to be able to look at the logs on that DC. To do that you first need to know what DC your need to connect to.

From the server you are having problems with, run the following very simple command to get this information.

echo %logonserver%

The logonserver in that command is surrounded with the % sign because it is a variable. This makes it possible to use that information in scripts etc.