Unknown Device (VMBUS) in Device manager in Virtual Machine for AVMA

Applies to: Windows 7 EnterpriseWindows Server 2008 EnterpriseWindows Server 2008 R2 Enterprise

Symptoms


On a Windows Server 2012 R2 Datacenter Hyper-V host, you may see 2 unknown device under Other Devices in device manager of any virtual machine running operating systems earlier than Windows Server 2012 R2.

If you view the properties of these devices and check driver details, Hardware IDs or Compatible IDs, they will show the following: 
  • vmbus\{4487b255-b88c-403f-bb51-d1f69cf17f87}
  • vmbus\{3375baf4-9e15-4b30-b765-67acb10d607b}
  • vmbus\{99221fa0-24ad-11e2-be98-001aa01bbf6e}
  • vmbus\{f8e65716-3cb3-4a06-9a60-1889c5cccab5}


Cause


These Virtual Devices (VDev) are provided for Automatic Virtual Machine Activation (AVMA) to communicate with the host. AVMA is only supported on virtual machines running Windows Server 2012 R2 or later versions of operating systems.

Resolution


The unknown devices are harmless and can be ignored. 

More Information


For more information about Automatic Virtual Machine Activation (AVMA) see the following:

http://technet.microsoft.com/en-us/library/dn303421.aspx