Can't Delete IP Address from Hyper-V Virtual Machine

Tuesday, June 1, 2010
I've had a number of problems with Windows Server 2008 Hyper-V guests that hold onto their original IPv4 address after running SysPrep. 

SysPrep is supposed to remove this kind of server-specific information, but for some reason this isn't happening with Server 2008 images.  Removal of machine-specific information is called "generalization" and is supposed to happen when you click the Generalize checkbox in SysPrep.

I've seen this cause the following symptoms:

"The IP address you have entered for this network adapter is already assigned to another adapter (microsoft Virtual machine Bus Network Adapter) which is no longer present in this computer"

For this error, do the following:
  • Open a command prompt and enter set devmgr_show_nonpresent_devices=1
  • Enter start devmgmt.msc to start Device Manager
  • In the Device Manager window, click View and Show hidden devices
  • Under Network Adapters you will see the dimmed conflicting device, probably the Microsoft Virtual Machine Bus Network Adapter.  Delete it and you can continue to configure the existing adapter.
The other issue I've seen is when the network adapter hangs onto the imaged machine's IP address and you cannot delete it.  In this case, you view the properties of the adapter and see the old IP address as an additional IP address.  It looks like you can successfully remove the old IP address, but it still shows up when you view the NIC's properties again.

In this case, you do the following from the Hyper-V host server:
  • Connect to the VM guest session from the host.  You will lose RDP connectivity otherwise.
  • Open Device Manager
  • Expand Network Adapters, right-click the misbehaving NIC and select Uninstall
  • Right-click Network Adapters and select Scan for hardware changes
  • Reconfigure the new adapter

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