Hello,

I have a single 2012 R2 STD server setup as an AD and simple file server.  

It's DNS randomly stops working. 

PCs on the network can ping internally by name, but cannot ping externally.

Starting and stopping the DNS service does not resolve the issue.

Rebooting just the server resolves the issue.

nslookup responds with DNS request timed out.

No errors in the event log, only an event 4013 warning.

Ipconfig on PCs points the DNS to the server.

Server updates have been applied.

Any thoughts?

Larry

Enable "debug logging" in the DNS and post the log.

Hi,

Am wondering how may DC and DNS server in your environment? All AD-Integrated zones?

You may confirm that if the KB below is applied to your problem:
https://support.microsoft.com/en-us/kb/2001093/

Besides, you may run dcdiag to check DC heath.

If the problem still exits, post theIpconfig /all result of your DNS server, and client.  

Best Regards,
Eve Wang