It might already exist in your event logs, export all the 12290 events and you have all their FQDN's which can be translated to IP via script.

http://technet.microsoft.com/en-us/library/ee939272.aspx

Quote from article

Event Viewer

Below you will see a snippet from the Key Management Service event log of our KMS host. This event,12290, shows that a KMS client contacted the host in order to attempt activation. There will be a12290 entry in the Key Management Service log on the KMS host system for each client that attempts to activate. If you don’t see this event for a client that you are troubleshooting, that client is not connecting to the KMS host.