Server Fault is a question and answer site for system and network administrators. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I just installed the Hyper-V role on my Windows Server 2012. It comes with something called a "Hyper-V extensible virtual switch". I assigned it to the only network card in my server. By doing so, the network card became useless/disabled/inactive/.. because the virtual switch disabled all features (IPv4, IPv6, Client for Microsoft Networks, ...) on the network adapter.

Can the extensible virtual switch be used in a single NIC configuration? If so, how do I configure the host network after enabling the virtual switch?

share|improve this question

In Windows Server 2008 R2 Hyper-V when using a single NIC and creating a Virtual Switch on that NIC, Hyper-V will create a virtual NIC that all of the networking components bind to and the physical NIC gets bound with the Microsoft Virtual Network Switch Protocol (which is the virtual switch driver). That shouldn't stop you from having normal network connectivity through the physical NIC.

In your case, the Hyper-V host and the Hyper-V guests will share the physical NIC. Make sure to check the check box on the Microsoft Virtual Switch that reads "Allow management operating system to share this network adapter".

That being said, at the very least you should have 2 network cards in the server: 1 dedicated for the host server and a second dedicated for the VM's.

I'm assuming all of the above is applicable in W2K12 and Hyper-V 2K12, or that it's very nearly applicable.

share|improve this answer
I did what you described but it didn't work. The problem was that I had VirtualBox installed. After uninstalling it, the virtual switch now works (see my answer). Is it possible that Hyper-V was confused by the virtual NIC that comes with VirtualBox? – Sebastian Krysmanski Nov 1 '12 at 6:56
It sounds like that could be the case. – joeqwerty Nov 1 '12 at 12:44
up vote 1 down vote accepted

The problem was that I had VirtualBox installed (but not running). After uninstalling VirtualBox, it now works as it should.

Note: All features (IPv4, ...) are still disabled on my physical NIC. Instead, the virtual switch takes over the features and settings (like static IP address) from the physical NIC and is now used for network traffic. The physical adapter is no longer used (directly).

share|improve this answer
The physical adapter is used, otherwise you wouldn't have phsical connectivity. All of the "intelligence" is move to the virtual NIC and the only thing bound to the physical NIC is the Microsoft Virtual Network Switch Protocol. Glad you got the problem sorted out. – joeqwerty Nov 1 '12 at 12:46
@joeqwerty Yes, that's what I meant. – Sebastian Krysmanski Nov 2 '12 at 5:45
The marked solution helped me a lot. I also had to open the virtual switch manager from the hyper-v console, because the virtual switch was attached to a logical network, not the physical device. – Gabor Farkas Dec 11 '12 at 8:54

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.