Hello,

We have three AD sites, each with Windows servers and much of them virtualized with Hyper-V (Windows Server Datacenter).

On two of our newest sites we have deployed Hyper-V hosts with Windows Server 2012.

Our main site is an older one with Hyper-V hosts running on Windows Server 2008 R2.

We are seeing duplicate NetBIOS name warnings each time we try to introduce a new computer to the domain or attempt to rename a computer.

For example:

"The following error occured validating the name "RA03".

A duplicate (potentially the shorter NETBIOS) name exists on the network."

Now, we know that this name has never been used on ANY of our computers (servers or otherwise).

This error is happening ONLY on our sites with Server 2012 Hyper-V hosts. Our main site with Server 2008 R2 infrastructure does not throw this error.

All our sites have different network gear (with only exception being the firewalls which are of same brand and provide IPsec tunneling between sites) which leads us to believe issue is not network equipment related.

Is there any possibility on finding out which particular device (for example, a mac address) claims to have the duplicate NETBIOS name?

Additionally, we are seeing event 4321 logged from NetBT source:

The name "RA03           :0" could not be registered on the interface with IP address 10.21.12.34. The computer with the IP address 89.236.12.34 did not allow the name to be claimed by this computer.

10.21.12.34 is the local computer whose domain membership and NETBIOS name is being changed.

89.236.12.34 is our firewall's external/outbound interface's publicly routably address.

(IP addresses changed for public forum posting)

We have local DNS and DHCP in-site.

We do not use WINS.

The 10.21.12.34 address is statically assigned (DHCP not enabled on the client computer).

you may be able to use the utility nbtstat.exe
http://technet.microsoft.com/en-us/library/cc757216(v=ws.10).aspx

also this article may help with diagnosis: http://support.microsoft.com/kb/822659/en-us

are you actually using WINS for name resolution within your network?
are you using it at the main/old site ?

duplicate-name errors can occur, if you do have multiple network connections (eg a laptop which is simultaneously connected to wired Ethernet and wireless Ethernet, and the two network connections are routing to each other, it can be a name-registration timing issue)