Networking Error, IP Address Already Assigned to Another Adapter

Under certain conditions, you may see the following error message from a Windows guest operating system:

The IP address XXX.XXX.XXX.XXX you have entered for this network adapter is already assigned to another adapter Name of adapter. Name of adapter is hidden from the network and Dial-up Connections folder because it is not physically in the computer or is a legacy adapter that is not working. If the same address is assigned to both adapters and they become active, only one of them will use this address. This may result in incorrect system configuration. Do you want to enter a different IP address for this adapter in the list of IP addresses in the advanced dialog box?

In this message, XXX.XXX.XXX.XXX is an IP address that you are trying to set and Name of adapter is the name of a network adapter that is present in the registry but hidden in Device Manager.

This can occur when you change a network connection's TCP/IP configuration from DHCP to a static IP address if:

• You have upgraded VMware virtual network adapters (for example when you migrate a virtual machine from an older to a new version of VMware software.)
• You have added and removed network adapters multiple times.

The cause of the error is that a network adapter with the same IP address is in the Windows registry but is hidden in the Device Manager (My Computer > Properties > Hardware > Device Manager). This hidden adapter is called a ghosted network adapter.

Using the Show hidden devices option in the Device Manager (View > Show hidden devices) does not always show the old virtual NIC (ghosted adapter) to which that IP Address is assigned

Microsoft addresses this issue in their Knowledge Base article 269155, which is available at the time of this writing at http://support.microsoft.com/?kbid=269155.

To resolve this problem, follow these steps to make the ghosted network adapter visible in the Device Manager and uninstall the ghosted network adapter from the registry:

1. Select Start > Run.
2. Enter cmd.exe and press Enter.
3. At the command prompt, run this command:
   
   set devmgr_show_nonpresent_devices=1
4. Enter Start DEVMGMT.MSC and press Enter to start Device Manager.
5. Select View > Show Hidden Devices.
6. Expand the Network Adapters tree (select the plus sign next to the Network adapters entry).
7. Right-click the dimmed network adapter, and then select Uninstall.
8. Close Device Manager.

1. Download the DevCon tool from Microsoft Knowledge Base: 311272 (http://support.microsoft.com/kb/311272/en-us).
2. Unpack the 32bit or 64bit DevCon tool binary to a local folder.
3. Click Start > Run.
4. Type cmd and press Enter.
5. Type CD:\path_to_binaries to navigate to the devcon.exe is located.
6. Use the following syntax to find installed network adapters:
   
   devcon findall *net* or
   devcon listclass net
   
   Note: In the output of the previous commands, there is a line for the ghosted network adapter that is similar to, PCI\.
7. Run the following command to remove the adapter:
   
   devcon remove @device\name
   
   For example, devcon remove "@PCI\VEN_14E4&DEV_1600&SUBSYS_01C21028&REV_02\4&378EDFA4&0&00E2" .  
    
   Note: IDs that include an ampersand character (&) must be enclosed in quotation marks as seen in the example.
    
8. Reboot the system and you no longer see the ghost network adapters.