Consider the following scenario:
You have a computer that is running Windows 8.1 or Windows Server 2012 R2.
You install 12 physical network interface controllers (NICs) on the computer.
You enable the Hyper-V role, you create 12 external virtual switches, and then you connect each virtual switch to a physical NIC.
You restart the computer.
In this scenario, one of the virtual switches may become disassociated from the NIC, and then it changes to an "Internal only" virtual switch.
To resolve this issue, remove the virtual switches, remove the Hyper-V role from the computer, and install update 2919355. Then, re-enable the Hyper-V role, and recreate the virtual switches. For more information about how to obtain update 2919355, click the following article number to view the article in the Microsoft Knowledge Base:
2919355 Windows RT 8.1, Windows 8.1, and Windows Server 2012 R2 Update April, 2014
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:
824684 Description of the standard terminology that is used to describe Microsoft software updates