How To Verify That Local SU Server Is Preferred

In previous (pre 10.8) iterations, Software Update Server would identify itself as the server that was supplying any updates. If you did not see the local server's name or IP address displayed, you could be relatively sure that your client had contacted the default Apple SU Server to query & download any available updates. With the advent of 10.8 and App Store as an intermediary I do not detect that my local SUS is supplying managed clients the available updates. I do not receive an error on the client machines and the updates are listed and installed, but how may I verify that they're coming from my LAN SU Server as has heretofore been the case?