I am trying to create hidden "mini-LANs" for use in testing application deployment and using VMware workstation on Vista x64 to create the machines.

Two instances of Windows XP are running. They both have single NICs on the NAT'ed virtual adapter VMnet8 and generally work fine with regard to the network. They can ping each other. A web server running on one can be accessed by the other. They can both access the Internet.

However, one of the machines is continually complaining about another machine on the network with a similar name. This prevents the other virtual machine from accessing its CIFS shares, for example:

net view \\NOT-A-DUP

System error 52 has occurred.

You were not connected because a duplicate name exists on the network. Go to System in Control Panel to change the computer name and try again.

I have tried changing the name as it suggests, but this does not help. Does anyone know why this error is occurring?


Are you using multiple copies of the same virtual machine file to bring up all of your test machines? If so, you may need to verify that VMWare is creating a new unique MAC address for each of the virtual machines as it comes online.

  • I do not think so. The machines have different MACs using ipconfig. Is it possible another VM on some other user's machines is conflicting, even behind NAT? – Jeremy Jul 2 '09 at 15:45

The problem may be related to using the name resolution mechanism provided by VMware Workstation. Let me explain.

I was configuring SQL Server on one of the VMs and having problems connecting from any machine other than the one hosting SQL Server. By accident, I noticed when pinging that the machine's name was resolving to rather than the VMs real address

With that info, I added another VM to host DNS and configured all the VMs to point at it for DNS rather than VMware Workstation's DNS proxy. All my network duplication problems went away and I could perform the NET VIEW command described above.

I would prefer a cleaner solution, but for now everything is working as I wanted.


Have you definitely changed the computer name and not just the computer description?

If you right-click My Computer and select properties, in the "computer name" tab you'll see a box labelled "computer description". This does not set the network name of the machine.

What you need to do is click the "change" button and edit the computer name in the dialogue box that comes up after that.

  • Good point. Yes, I verified the name is actually different. It is definitely not a duplicate too. – Jeremy Jul 2 '09 at 15:25
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    Check the output from "echo %COMPUTERNAME%" on each of the VMs to make sure that Windows has acknowledged the name change(s). The machine may also have identical UUIDs which will cause problems as it will make VMWare assign them both the same MAC address, see vmware.com/support/gsx3/doc/manage_uuid_gsx.html for more info. – David Spillett Jul 2 '09 at 15:57
  • Following instructions I googled, I forced the VMs to regenerate their UUID and MAC. Still getting the error though. Thanks for the suggestions! – Jeremy Jul 2 '09 at 18:45

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