Friday, November 4, 2011

Cluster Validation Error due to duplicate NIC GUIDs

If you are running a Windows 2008 R2 Failover Cluster, you may see the following error when running the Failover Cluster Validation tests:

 It tells:

Validate Windows Firewall Configuration
Validate that the Windows Firewall is properly configured to allow failover cluster network communication.
Validating that Windows Firewall is properly configured to allow failover cluster network communication.
An error occurred while executing the test.
There was an error verifying the firewall configuration.
An item with the same key has already been added.

The last line is telling us that two elements have the same value. These elements are the Network adapters and the offending value are the adapter GUIDs. These GUIDs should be unique but if you have cloned your servers or if your Cluster servers are cloned VMWare Virtual Machines, this error might occur.

To solve this issue, start by running a Powershell session, then run the following command on every Cluster node and compare the GUID of your Network adapters:
 
Get-WmiObject Win32_NetworkAdapter | format-list Name,GUID

You should see that the Network adapters have the same GUID on different servers.

If this is your case, uninstall all of your Network adapters from Device Manager from all the Cluster members except one (but first note your IP address configuration!). Reboot them, re-run the Powershell command and you should find that your Network adapters are back with brand new GUIDs (thanks Plug and Play!).

Re-run the Cluster Validation Report and everything should be OK.

Please leave a comment if this post helped you!

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