By switching from the default VMware OUI to range- or prefixed-based MAC address allocation through the vSphere 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 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.

Note

You should use prefix-based MAC address allocation in vCenter Server 5.1 and ESXi hosts 5.1, and later.

If a vCenter Server 5.1 manages pre-5.1 ESXi hosts, use VMware OUI prefix-based MAC address allocation. Virtual machines assigned non-VMware OUI prefixed MAC addresses fail to power on on the pre-5.1 hosts. These hosts explicitly validate if an assigned MAC address uses the VMware OUI 00:50:56 prefix.

1

In the vSphere Client, select Administration > vCenter Server Settings.

2

Select Advanced Settings.

3

Depending on the target allocation type add or edit the following parameters.

Use only one allocation type.

Change to prefix-based allocation.

Key

Example Value

config.vpxd.macAllocScheme.prefixScheme.prefix

005026

config.vpxd.macAllocScheme.prefixScheme.prefixLength

23

prefix and prefixLength determine the range of MAC address prefixes which newly-added vNICs have. prefix is the starting OUI of MAC addresses related to the vCenter Server instance, and prefixLength determines how many bits the prefix is long.

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

Change to range-based allocation.

Key

Example Value

config.vpxd.macAllocScheme.rangeScheme.range[X].begin

005067000000

config.vpxd.macAllocScheme.rangeScheme.range[X].end

005067ffffff

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.

4

Click OK.