The last octet (ff) is automatically generated from the range 0x0-0xFF.īecause the last octet is an 8-bit value, there is a default limit of 256 possible MAC addresses.The next two octets (dd-ee) are derived from the last two octets of the server's IP address.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.Hyper-V generates the MAC address as described below (mapping MAC address to aa-bb-cc-dd-ee-ff): This problem occurs because the default number of dynamic MAC addresses for virtual machines (256) has been exceeded.
On a Windows Server 2008 or Windows Server 2008 R2 Hyper-V host, an Event ID 12565 from source "Microsoft-Windows-Hyper-V-Worker" is logged, as described in the Event ID 12565 - NIC Configuration. Synthetic Ethernet Port (Instance ID CCE417C5-BDD9-4216-85CA-248620EE75C6): Failed to power on with Error 'Attempt to access invalid address'. The application encountered an error while attempting to change the state of '' When you start a guest virtual machine, you may encounter the following error message: The Hyper-V server is configured to provide Dynamic MAC addresses to the guest machines. The server uses this number to generate the next MAC address from the pool. You have a Windows Server 2012 computer that is configured with the Hyper-V role. Last MAC address used The MAC address that precedes the first MAC address in the pool (in this example it is 00:50:56:00:00:00). This article provides a solution to an issue that occurs when you start a guest virtual machine.Īpplies to: Windows Server 2012 R2 Original KB number: 2804678 Symptoms