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Table Of Contents
Prefix-based MAC address allocation overcomes the limits of the default VMware allocation to provide
unique addresses in larger scale deployments. Introducing an LAA prefix leads to a very large MAC
address space (2 to the power of 46) instead of an universally unique address OUI which can give only
16 million MAC addresses.
Verify that the prefixes that you provide for different vCenter Server instances in the same network are
unique. vCenter Server relies on the prefixes to avoid MAC address duplication issues. See the vSphere
Troubleshooting documentation.
Range-Based MAC Address Allocation
You can use range-based allocation to include or exclude ranges of Locally Administered Addresses
(LAA).
You specify one or more ranges using a starting and ending MAC addresses, for example,
(02:50:68:00:00:02, 02:50:68:00:00:FF). MAC addresses are generated only from within the
specified range.
You can specify multiple ranges of LAA, and vCenter Server tracks the number of used addresses for
each range. vCenter Server allocates MAC addresses from the first range that still has addresses
available. vCenter Server checks for MAC address conflicts within its ranges.
When using range-based allocation, you must provide different instances of vCenter Server with ranges
that do not overlap. vCenter Server does not detect ranges that might be in conflict with other
vCenter Server instances. See the vSphere Troubleshooting documentation for more information about
resolving issues with duplicate MAC addresses.
Assigning a MAC Address
Use the vSphere Web Client to enable prefix-based or range-based MAC address allocation and to adjust
the allocation parameters.
If you are changing from one type of allocation to another, for example changing from the VMware OUI
allocation to a range-based allocation, use the vSphere Web Client. However, when a schema is prefix-
based or range-based and you want to change to a different allocation schema, you must edit the
vpxd.cfd file manually and restart vCenter Server.
Change to or Adjust Range- or Prefixed-Based Allocations
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.
vSphere Networking
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