Prior to Windows Server 2012 R2 Hyper-V there was a PXE issue that meant you needed to have a legacy NIC boot PXE then a synthetic NIC for speed, which the PVS would auto switch on boot. This is now gone.
This was the PVS v7+ setting:
By default, Provisioning Services automatically switches from legacy Hyper-V NICs to synthetic NICs if both exist in the same subnet. To enable the option to only use synthetic NICs if legacy Hyper-V NICs exist within the same subnet, edit the target device's registry settings:
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\BNIStack\Parameters] "DisableHyperVLegacyNic"=dword:00000000
Windows Server 2012 R2 Hyper-V
Generation 2 Virtual Machines now have this support:
The synthetic NIC can boot from the network using PXE
Synthetic network adapters support PXE boot. Gone is the old legacy network adapter.
