Hyper-V guests - loss of network connectivity requiring reboot of Hyper-V host.

Hello,

I have recently introduced a Windows 2012R2 Hyper-V host server (Version 6.3.9600.16384).  This server hosts 2 Windows 2012R2 guest machines, one which will be a domain controller & file share, whilst the other will be the Exchange 2013 server.  The server is not in full production yet but will be soon.  

Early this morning we found that the guest Operating Systems no longer had network connectivity.  I could not ping them from any other machine on the network.  However the guest machine were able to ping each other.  Once I restarted the host server all network connectivity was back to normal.  

I checked the Event Viewer on the host server but was unable to find any Events that corresponded to this.  EV was quite clean.  Consequently I am unsure as to how to determine what could have caused the issue.  This would be the time that I can take any proactive action to prevent a full outage once the servers are in full production.

Any suggestions as to what I could look for?  What could cause this sort of thing?  This is the first time I have encountered this in the last 2 weeks since the servers have been put in place.

Any suggestions would be greatly welcome.

Thanks in advance.

Regards,

Real-Timer