Have a Windows SBS 2011 with Exchange that is handling all DNS for the network.
Since getting a 3rd party (Hardware & Support) to setup a recieving FTP service and restricting Exchanges memory useage for another 3rd party product (Stock software) the local network seems to periodically 'lose the internet connection'.
Delving deeper I found that the DNS service is somehow failing/stopping without the actual service on the server reporting such (nothing in event logs). A simple restart of the 'DNS Role' on the server solves the problem.
The manager onsite reports that he has to do this most days in the afternoon - yet not at the same time and other days it works fine without a restart being required.
I'm unable (lacking sufficient SBS2011 knowledge) to diagnose this further, ideally I would like the DNS Role to report (and log) the failure, then automatically restart itself.