You have a Windows Server 2012 computer which is configured with the Hyper-V role. The Hyper-V server is configured to provide Dynamic MAC addresses to the guest machines.
When you start a guest virtual machine, you may encounter the following error message:
Hyper-V generates the MAC address as described below (mapping MAC address to aa-bb-cc-dd-ee-ff):
- The first three octets (aa-bb-cc) are Microsoft's IEEE organizationally Unique Identifier, 00:15:5D (which is common on all Hyper-V hosts.
- The next two octets (dd-ee) are derived from the last two octets of the server's IP address.
- The last octet (ff) is automatically generated from the range 0x0-0xFF.
Because the last octet is an 8-bit value, there is a default limit of 256 possible MAC addresses.
a) Turn off the virtual machine, allocate a static MAC Address that does not belong to Hyper-V's dynamic MAC address range, then restart the virtual machine.
b) Increase the range of MAC addresses by using one of the following methods, by modifying the fifth and/or the sixth octet of the default dynamic MAC address range:
If the host is Windows Server 2008, you can modify the dynamic MAC address range via the following registry values:
If the host is Windows server 2008 R2, you can use the Virtual Network Manager GUI, as documented in the following MSDN blog post:
Hyper-V R2: MAC Address Management
Note: Knowledge of the hexadecimal numbering system is helpful to modify the octets. Each octet's range is 00 - FF.