I am running a fully updated Windows Server 2012 Datacenter with several guest Hyper-Vs. I updated the host OS and rebooted. The guest VMs are set to save and restart automatically on reboot. All the Server 2012 Datacenter Guest VMs started but there was
no network connectivity. It showed a red X in the tray and was unable to get an IP address. Using the troubleshooter does not resolve the issue as it says to plug in a network cable. However disabling and re-enabling the device resolves it or rebooting the
VM. The Server 2012 Standard VMs do not appear to be affected.
This has also happened when trying to use a VPN client and it breaking the built in network connection causing the same problem although that has not happened consistently.
check to see if you have the most current integration services installed, insert the disk and it will tell you if it wants to upgrade the software, if you highlight the VM and look at the network status tab does it say degraded?
are you using teamed adapters? or multihomed adapters?
Check and make sure you didn't assign ip addresses to your virtual switches, I've see the network troubleshooter do this. the only service that should be enabled on the physical network cards is "Hyper V extensible switch"
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