Unknown Device (VMBUS) appears in Device manager in Virtual Machine

On Windows-based virtual machines that are running on a Windows Server based Hyper-V host, you may see unknown devices under Other Devices in device manager.

Applies to:   Windows 7 Service Pack 1, Windows Server 2012 R2, Windows Server 2016, Windows Server 2019
Original KB number:   2925727

Unknown devices

When you view the properties of these devices and check driver details, Hardware IDs, or Compatible IDs, they may show the following IDs:

  • vmbus\{4487b255-b88c-403f-bb51-d1f69cf17f87}
  • vmbus\{3375baf4-9e15-4b30-b765-67acb10d607b}
  • vmbus\{99221fa0-24ad-11e2-be98-001aa01bbf6e}
  • vmbus\{f8e65716-3cb3-4a06-9a60-1889c5cccab5}

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.

Or, the device may show the following IDs:

  • vmbus\{c376c1c3-d276-48d2-90a9-c04748072c60}
  • vmbus\{c4e5e7d1-d748-4afc-979d-683167910a55}

The device is for Initial Machine Config (IMC) for the virtual machines. There could be various other causes that could lead this issue.

More information

The unknown devices are harmless and can be safely ignored.


For more information about Automatic Virtual Machine Activation (AVMA), see Automatic Virtual Machine Activation in Windows Server: