Hyper-V Server Management from Windows 8.1

We used to have a problem like this where I'm at. I don't remember the exact details, but the final solution had to do with a conflicting mac address assigned dynamically to a virtual network adapter. Pinning those down so they weren't dynamic helped a lot. You normally don't want to do that because it can make it harder to move a virtual machine to a different host, but it helped us in this instance.

The other part is the physical nics were made by broadcom and we also had a configuration error there, where a previous admin had tried incorrectly to use the broadcom utility to trunk the two nics together on the host for improved bandwidth/throughput. We removed that setup and configured one of the nics so it had no IP at all on the host machine, but could still be used for passthrough to virtual guests. Then we set each virtual machine to only use one nic or the other, balancing the load based on historical traffic. Of course that means no failover if an adapter or connection goes down, and we haven't followed through well to see whether traffic has remained balanced over time, but it's been rock solid stable since then.

You can exclude certain nics from NLA (Network Location Awareness). Very common to do this in VMware workstation scenarios since the VMware nics always end up as unidentified/public. Here's how:

1. Navigate to:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E972-E325-11CE-BFC1-08002BE10318}
2. You will find enumerated keys like 0000, 0001, 0002 and so on.
3. Expend them one by one and look for DriverDesc REG_SZ value data.
4. In the same registry key where you found the name of the nic to exclude (DriverDesc value), create another new DWORD Value, name it *NdisDeviceType (it Case Sensitive!!). Double click on this value and in "Value Data" field put 1 as Decimal data

(snipped from) http://www.petri.co.il/forums/showthread.php?t=45181