Specifications

CHAPTER 7 Networking
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Maintaining and Changing the MAC Address
of a Virtual Machine
When a virtual machine is powered on, GSX Server automatically assigns each of its
virtual network adapters an Ethernet MAC address. MAC stands for media access
control. A MAC address is the unique address assigned to each Ethernet device.
The software guarantees that virtual machines are assigned unique MAC addresses
within a given host system. In most cases, the virtual machine is assigned the same
MAC address every time it is powered on, so long as the virtual machine is not moved
(the path and filename for the virtual machine’s configuration file must remain the
same) and no changes are made to certain settings in that file.
In addition, GSX Server does its best, but cannot guarantee, to automatically assign
unique MAC addresses for virtual machines running on multiple host systems.
Avoiding MAC Address Changes
To avoid changes in the MAC address automatically assigned to a virtual machine, you
must not move the virtual machine’s configuration file. Moving it to a different host
computer or even moving it to a different location on the same host computer
changes the MAC address.
You also need to be sure not to change certain settings in the virtual machine’s
configuration files. If you never edit the configuration file by hand and do not remove
the virtual Ethernet adapter, these settings remain untouched. If you do edit the
configuration file by hand, be sure not to remove or change the following options:
ethernet[n].generatedAddress
ethernet[n].addressType
ethernet[n].generatedAddressOffset
uuid.location
uuid.bios
ethernet[n].present
In these options, [n] is the number of the virtual Ethernet adapter, for example
ethernet0.
Note: To preserve a virtual Ethernet adapter’s MAC address, you also must be careful
not to remove it. If you remove the adapter, then recreate it, it may receive a different
MAC address.
Manually Assigning a MAC Address
If you want to guarantee that the same MAC address is assigned to a given virtual
machine every time, even if the virtual machine is moved, or if you want to guarantee