If you use a range- or prefixed-based allocation, you can use the vSphere Client to adjust the parameters of your allocation.

To change allocation schemes from VMware OUI to a range- or prefixed-based allocation, you must add a key and default value to Advanced Settings. If you already added the key and default values, use Advanced Settings to adjust the parameters for each key.

To change from a range- or prefixed-based allocation to the VMware OUI allocation, you cannot use the vSphere Client. You must edit the vpxd.cfg file manually. VMware recommends changing allocation types through the vSphere Client because editing files can introduce errors. For information about editing the vpxd.cfg file, see the vSphere Networking publication.


Prefix-based MAC address allocation is only supported invCenter Server 5.1 and 5.1 hosts. If you add pre-5.1 hosts to vCenter Server 5.1 , and use anything other than VMware OUI prefix-based MAC address allocation, virtual machines assigned non-VMware OUI prefixed MAC addresses fail to power on their pre-5.1 hosts.

The prefix-based MAC address allocation schemes are not supported on pre-5.1 hosts because pre-5.1 hosts explicitly validate if an assigned MAC address uses the VMware OUI 00:50:56 prefix. If the MAC address is not prefixed with 00:50:56, the virtual machine pre-5.1 host fails to power on.


Launch the vSphere Client and log in to a vCenter Server system.


  1. In the vSphere Client, select Administration > Server Settings.
  2. Select Advanced Settings.
  3. Add or adjust one of the following allocation types.
    Note: Use only one allocation type.
    • Prefix-based allocation
      Key Default Value
      config.vpxd.macAllocScheme.prefixScheme.prefix 005026
      config.vpxd.macAllocScheme.prefixScheme.prefixLength 23
      Change the default values to your choice of prefix and prefix length.
    • Range-based allocation
      Key Default Value
      config.vpxd.macAllocScheme.rangeScheme.range[0].begin 005067000000
      config.vpxd.macAllocScheme.rangeScheme.range[0].end 005067ffffff
      Change the default values to the allocation range of your choice. Replace [0] with the range ID of your choice.
  4. Click OK.