Syed Jahanzaib Personal Blog to Share Knowledge !

December 6, 2013

ESXI 5.5 static mac address “conflicts with VMware reserved MACs”

Filed under: VMware Related — Tags: , , — Syed Jahanzaib / Pinochio~:) @ 11:36 AM



You may see above error in ESXI 5.5 after changing dynamically generated MAC address to STATIC mac address dueto application MAC bind restriction.

In new ESXI 5.5 ,  new policies have been added where the statically assigned MAC addresses can only be in the range 00:50:56:xx:xx:xx series, If you try to change it to something else and then power on the guest machine, you may see above error.

Few days before, a friend of mine upgraded his ESXI from ver 5.0 to 5.5. One of his guest application was binded with the MAC address and the new esxi 5.5 doesn’t allow to use that specific series mac address. So I googled and found following solution that worked (at least for me 😉 )

To RESOLVE this issue, follow this.

1- Enable SSH in ESXI Server Configuration

2- Turn off the target guest machine and change the mac address as per your requirements for the required interface.

3- Turn off the V-Sphere ESXI client.

3- Login to ESXI server via SSH using any ssh client like PUTTY

4- Goto your data store / guest machine folder and open the VMX file.


For example I have guest machine with ‘123‘ name. So I used following

~ # cd /vmfs/volumes/
/vmfs/volumes # ls

52a18cdd-49376389-86aa-000c29d1de32  61031d71-0233e8da-be74-f942274c16c3
52a18ce5-9d0863e6-e50b-000c29d1de32  8901537a-ad66db83-fd1f-38ac926cce01
52a18ce7-bd9d6e2a-dacf-000c29d1de32  datastore1
/vmfs/volumes #

/vmfs/volumes # cd datastore1/
/vmfs/volumes/52a18ce5-9d0863e6-e50b-000c29d1de32 # ls

/vmfs/volumes/52a18ce5-9d0863e6-e50b-000c29d1de32 # cd 123
/vmfs/volumes/52a18ce5-9d0863e6-e50b-000c29d1de32/123 # ls

123-flat.vmdk               vmware-14.log
123.nvram                     123.vmxf                      vmware-15.log
123.vmdk                      vmware-11.log                 vmware-16.log
123.vmsd                      vmware-12.log                 vmware.log
123.vmx                       vmware-13.log

As showed in the image below . . .


Now open the VMX file of the guest machine.

for example

vi 123.vmx

now press I and add this line anywhere.

ethernet0.checkMACAddress = "false"

(Change the ethernet0 to match your local ethernet number)

Now save and exit it by pressing :wq

Now start V-Sphere ESXI client and start the machine as you normally do 🙂

Congrats you are UP with new MAC address activated 😀


Following is an sample of working .vmx file for static mac address.

ethernet0.networkName = "LAN"
ethernet0.addressType = "static"
ethernet0.present = "TRUE"
ethernet0.checkMACAddress = "false"
ethernet0.address = "00:0C:29:Ha:Ha:Ho"

Syed Jahanzaib


  1. hi, I have many wireless station connected to a base, i use the dude program to monitor my network, all the station use RB433AH please help me to display the voltage for each router board and the ccq for each wireless XR5 ubquity pci board. thx a lot for your coorporation.

    Date: Fri, 6 Dec 2013 06:36:25 +0000


    Comment by a b — December 8, 2013 @ 11:16 AM

  2. Thank you very much for your post. Adding ethernet0.checkMACAddress = “false” worked for me. I was able to retain the old MAC address.


    Comment by Mike — March 24, 2015 @ 5:03 AM

  3. Genius.


    Comment by Dave — September 1, 2015 @ 6:53 AM

  4. This method did not work for me at first, then I realized that the server would need to be un-registered from it’s host in VSphere Client or VCS and then after the changes made to the vmx file, the server would need to be re-registered to the same or different host (depending on shared storage config). After I added those two steps, this worked like a charm! Thanks – thought I had a bigger battle on my hands and your method worked great.


    Comment by ATP — February 9, 2016 @ 10:22 PM

  5. Great!
    this solution works for me. Thank you very much!


    Comment by James — April 29, 2016 @ 7:49 AM

  6. ESX5.5 U2 makes this little bit more complicated.
    The .CheckMacAddress alone didn’t work for me

    There we need to change the .addresstype from “static” to “generated”
    and I had to change .Address to GeneratedAddress

    Mainly I had added the E1000, removed it and wanted to add the VMXNET3 with the same mac addresss because I already had a static DHCP entry for that address I didnt want to change…


    Comment by Andreas G. — March 8, 2017 @ 2:23 AM

  7. Amazing! Thanks so very much. Worked perfectly for me.


    Comment by Timothy Giese — May 2, 2018 @ 9:02 PM

  8. Or just use the client and browse the datastore, download the vmx you want to edit, edit with wordpad, upload in place, run the VM


    Comment by Chris Jarvis — June 1, 2018 @ 9:12 AM

  9. thanks, it worked for me!


    Comment by kazi — April 13, 2020 @ 12:27 PM

    • be aware that some editions of ESX do restrict the mac address usage afterwards, because VMware wants to keep the vendor ID (the first three hex numbers) to prevent MAC spoofing. But some applications are bound to specific MAC addresses and doing P2V without hardware passthorugh to the original network device the application will cease working… e.g. Tobit David 6

      Liked by 1 person

      Comment by Erwin — April 23, 2020 @ 2:28 PM

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