By switching from the default VMware OUI to range- or prefixed-based MAC address allocation through the vSphere Web Client, you can avoid and resolve MAC address duplication conflicts in vSphere deployments.

Change the allocation scheme from the default VMware OUI to range- or to prefixed-based allocation by using the Advanced Settings available for the vCenter Server instance in the vSphere Web Client.

To switch from range- or prefixed-based allocation back to VMware OUI allocation, or between range- and prefixed-based allocation, edit the vpxd.cfg file manually. See Set or Change Allocation Type.


  1. In the vSphere Web Client, navigate to a vCenter Server instance.
  2. On the Configure tab, expand Settings and select Advanced Settings.
  3. Click Edit.
  4. Add or edit parameters for the target allocation type.

    Use only one allocation type.

    • Change to prefix-based allocation.


      Example Value





      prefix and prefixLength determine the range of MAC address prefixes that newly added vNICs have. prefix is the starting OUI of MAC addresses related to the vCenter Server instance, and prefixLength determines the length of the prefix in bits.

      For example, the settings from the table result in VM NIC MAC addresses starting with 00:50:26 or 00:50:27.

    • Change to range-based allocation.


      Example Value





      X in range[X] stands for the range sequence number. For example, 0 in range[0] represents the allocation settings of the first range for MAC address allocation.

  5. Click OK.