Installation guide

CHAPTER 11 Networking
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Once the MAC address has been generated, it does not change, unless the virtual
machine is moved to a different location; for example, a different path on the same
server or a different ESX Server machine. We save the MAC address in the
configuration file of the virtual machine.
ESX Server keeps track of all MAC addresses that have been assigned to network
adapters of running and suspended virtual machines on a given physical machine.
ESX Server ensures that the virtual network adapters of all of these virtual machines
have unique MAC addresses.
The MAC address of a powered-off virtual machine is not checked against running or
suspended virtual machines. Therefore it is possible, but unlikely, that when a virtual
machine is powered on again, it can get a different MAC address. This is due to a
conflict with a virtual machine that was powered on when this virtual machine was
powered off.
Setting MAC Addresses Manually
In order to work around both the limit of 256 virtual network adapters per physical
machine and possible MAC address conflicts between virtual machines, the MAC
addresses can be assigned manually by system administrators. VMware uses a
different OUI for manually generated addresses: 00:50:56. The MAC address range is
00:50:56:00:00:00-00:50:56:3F:FF:FF.
You can set the addresses by adding the following line to a virtual machine’s
configuration file:
ethernet<number>.address = 00:50:56:XX:YY:ZZ
where <number> refers to the number of the Ethernet adapter, XX is a valid hex
number between 00 and 3F, and YY and ZZ are valid hex numbers between 00 and
FF. The value for XX must not be greater than 3F in order to avoid conflict with MAC
addresses that are generated by the VMware Workstation and VMware GSX Server
products. Thus the maximum value for a manually generated MAC address is
ethernet<number>.address = 00:50:56:3F:FF:FF
You must also set the option in a virtual machine’s configuration file:
ethernet<number>.addressType="static"
VMware ESX Server virtual machines do not support arbitrary MAC addresses, hence
the above format must be used. So long as you choose XX:YY:ZZ uniquely among
your hard-coded addresses, conflicts between the automatically assigned MAC
addresses and the manually assigned ones should never occur.