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If the vCenter Server instance generates the MAC addresses of virtual machines according to the
default allocation, VMware OUI, change the vCenter Server instance ID or use another allocation
method to resolve conflicts.
Note Changing the vCenter Server instance ID or switching to a different allocation scheme does
not resolve MAC address conflicts in existing virtual machines. Only virtual machines created or
network adapters added after the change receive addresses according to the new scheme.
For information about MAC address allocation schemes and setup, see the vSphere Networking
documentation.
Solution Description
Change the vCenter Server ID You can keep using the VMware OUI allocation scheme if your deployment
contains a small number of vCenter Server instances. According to this scheme,
a MAC address has the following format:
00:50:56:XX:YY:ZZ
where 00:50:56 represents the VMware OUI, XX is calculated as (80 +
vCenter Server ID), and YY:ZZ is a random number.
To change the vCenter Server ID, configure the vCenter Server unique ID option
in the Runtime Settings section from the General settings of the vCenter Server
instance and restart it.
The VMware OUI allocation works with up to 64 vCenter Server instances and is
suitable for small scale deployments.
Switch to prefix-based allocation You can use a custom OUI. For example, for a 02:12:34 locally administered
address range, MAC addresses have the form 02:12:34:XX:YY:ZZ. You can use
the fourth octet XX to distribute the OUI address space between the
vCenter Server instances. This structure results in 255 address clusters, each
cluster managed by a vCenter Server instance, and in about 65000 MAC
addresses per vCenter Server. For example, 02:12:34:01:YY:ZZ for vCenter
Server A, 02:12:34:02:YY:ZZ for vCenter Server B, and so on.
Prefix-based allocation is suitable for deployments of a larger scale.
For globally unique MAC addresses, the OUI must be registered in IEEE.
a Configure MAC address allocation.
b Apply the new MAC address allocation scheme to an existing virtual machine in its Virtual
Hardware settings.
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Power off a virtual machine, configure the adapter to use a manual MAC address, revert to
automatic MAC address allocation, and power on the virtual machine.
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If the virtual machine is in production and you cannot power it off for configuration, after you
change the vCenter Server ID or the address allocation scheme, re-create the network
adapter in conflict with enabled automatic MAC address assignment. In the guest operating
system, set the same static IP address to the re-added adapter as before.
vSphere Networking
VMware, Inc. 255