Manual MAC address for a VMware guest | Rickard Andersson

Manual MAC address for a VMware guest

If you’ve ever tried to manually specify a MAC address for a VMware ESX virtual machine, you might have encountered the error message:

The MAC address entered is not in the valid range. Valid values are between 00:50:56:00:00:00 and 00:50:56:3f:ff:ff.

The reasons why VMware force manual MAC addresses into this scope are unclear to me (probably to prevent collisions), but regardless, it can be an issue. I needed to specify a particular MAC address in the 00:04 range. The reason being we were retiring an old physical server running the FLEXlm licensing service and the licenses were granted for the MAC address of the NIC on that machine. Renewing the licenses for the new virtual machine turned out to be ridiculously expensive so our only real option was to “spoof” the MAC address.

I then ran into the aforementioned issue. However, the problem was easily solved by setting the MAC address from within the guest operating system instead. In this case, the server was running Windows Server 2003 and changing the MAC address was as simple as modifying the parameter “networkaddress” in the properties for the NIC in device manager. Voila!


  1. Chad
    Posted April 29, 2009 at 16:03 | Permalink

    Hey, I have the exact same issue. I have an old legacy Win2k server with FLEXlm on it. I did a P2V into ESXi 3.5. After I set the MAC address as you did I lost my network connectivity. A reboot didn’t help. I was wondering if you also reconfigured anything at the VM level for the MAC or did you leave those settings at the defaults (auto MAC). Other thoughts?


  2. Posted April 29, 2009 at 16:15 | Permalink

    Hi Chad,

    I left it at auto at the VM level. The only difference between the two scenarios seems to be that I did not import the physical machine, but instead set up a fresh 2003 server from a template. I would try that to make sure it isn’t a 2000 server issue.


  3. Jim
    Posted June 17, 2010 at 21:31 | Permalink

    I was able to get this work but I had to change the nic in the vm from the vmxnet 3 adapter to the e1000 adapter. The e1000 adapter actually has a setting in the driver advanced tab that lets you set a mac address. The setting is called Locally Administered Address

  4. Joe
    Posted August 4, 2010 at 16:52 | Permalink

    Jim, you’re brilliant. I couldn’t get the VMXnet3 adapter to accept the spoofed MAC, but the E1000 did the trick. Thanks for the idea!

  5. pablo
    Posted December 16, 2010 at 21:34 | Permalink

    you can also put

    ethernetX.checkMACAddress = “false”

    in the vm’s configuration file, to prevent checking of MACs.

  6. anonymous
    Posted April 1, 2011 at 20:14 | Permalink

    Jim’s post worked for me.

  7. Daniel
    Posted May 18, 2011 at 21:47 | Permalink

    I also was able to use the E1000 to set the locally administered address, but after a reboot FlexLM complained about the MAC address not matching. After checking the lmrgdlogs, indeed FlexLM only saw the VM’s auto-populated MAC address and NOT the custom locally administered one I entered. Anyone else run into this problem?

  8. jbongrand
    Posted September 9, 2011 at 12:14 | Permalink

    Hi Daniel,
    Just do it right now. Flexlm is starting normally after forcing the MAC on the E1000.
    Version of flexlm is 9.5.0 if it could make difference.
    Also, depending on vendors, the license file could have the MAC and/or the volume ID of the C: drive to check against. You could change it by using Volume ID from Mark Russinovitch (now Microsoft) at


  9. bish
    Posted October 14, 2011 at 04:33 | Permalink

    @pablo That setting doesn’t seem to permit the user to change the MAC in the GUI to even a 00:0c:29 kind of old-school VMware mac. It used to, but not any more.

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