No network connectivity for VMs with tagged VLANs after upgrade to W2K12 R2

Hi all

I have a lab consisting of 2 Mac Mini Servers, late 2009 model, most often running Hyper-V on the newest evaluation versions of Windows Server. With Windows Server 2012, everything was running smoothly.After upgrading to Windows Server 2012 R2, all VMs that are assigned to a VLAN lost network connectivity (aka "Enable virtual LAN identification" in the VM NIC settings). VMs using no vlan id work as expected!

While doing research it seems like there are some network-related problems with W2K12 R2 floating around, but I was unable to find any useful info matching my problem.

Installing W2K12 R2 Update 1 did not help in any way. After quite some hours with eliminating possible problem sources, I seem to end up with this behavior being a BUG in Windows Server 2012 R2.

Here some details for anybody willing to doublecheck that I did not overlook anything:

: both servers are configured identically. The build-in NIC is assigned to a virtual switch of type "External", and is shared with the management OS. Each host has an additional FastEthernet USB adapter, which is also configured as virtual switch of type "External", but not shared with the OS.

is configured to send untagged traffic for the management network, and tagged traffic for all VM networks, on all ports that are connected to the lab server (meaning both for the built-in and for the USB network adapter). The switch config was not touched in the OS upgrade process.

1. When setting "Enable virtual LAN identification for management operating system" and re-configuring the switch to send tagged traffic also for management network, then the management OS also looses network connectivity.

2. Un-checking the "Allow management operating system to share this networking adapter" does not help either. When running Get-NetAdapter I see that the physical adapter (Ethernet) has the same MAC-address as the virtual adapter (vEthernet), as somewhat described here.

3. Attaching the VMs to the vitual switch using the USB network adapter does not help either, so I am inclined to rule out a driver related problem since the problem show on two completely different NICS - unless Microsoft somewhat has made changes to VLAN traffic handling in Hyper-V/virtual switch!

as VEN_10DE / DEV_0AB0, and according to pcidatabase.com this is the "NForce 9300 LAN/SATA/SMBUS/SMU/GPU" controller. Device Manager reports it as "NVIDIA nForce Networking Controller Properties", driver version 7.3.1.7336 from 23.02.2012. When checking the NIC configuration (Device Manager/NVIDIA .. Network Controller, Properties, Advanced), I see that the propertyPriority & VLAN with value ofPriority Enabled. When changing this toPriority & VLAN Enabled, management OS also looses network connectivity. The VMs still do not have any network connectivity. - In short: it seems like Window Server 2012 R2 has - at least in my lab scenario - a serious problem handling any VLAN-related traffic. Windows Server 2012 was working flawlessly. Any hints appreciated, or some feedback if other are experiencing similar issues.