| Event Id | 12561 |
| Source | Microsoft-Windows-Hyper-V-VStack-SynthNic |
| Description | Static MAC address %5 for "%4" is invalid. |
| Event Information | According to Microsoft : Cause : This event is logged when Static MAC address is invalid. Resolution : Reconfigure static MAC address By default, new virtual machines in Hyper-V are created with NICs that are assigned dynamic MAC addresses. If virtual machines with identical static MAC addresses are run at the same time, virtual machine networking may not work properly. For virtual machines that share a virtualization server (also called a host), static MAC address conflicts are rarely an issue. However, if multiple servers with the Hyper-V role enabled are used, you must ensure that the address ranges are unique and managed across the servers. You can use System Center Virtual Machine Manager to do this. Turn Off the virtual machine and change the Static MAC Address of the NIC to a value that is not duplicated in another NIC on the network or out of the allowed range. Alternatively, change the Static MAC Address of the NIC to a Dynamic MAC Address. If a virtual machine with a dynamic MAC address is copied to another computer, it will be assigned a new, unused MAC address. Note: Turning off a virtual machine is equivalent to powering off a computer, so data loss is possible. To perform these procedures, you must have membership in Administrators on the virtual machine, or you must have been delegated the appropriate authority. To determine the MAC address: 1. On the virtual machine, open an elevated Command Prompt window, click Start 2. On the Start menu, point to All Programs, click Accessories, right-click Command Prompt, and then click Run as administrator. 3. On the command line type: ipconfig /all 4. Note the static MAC address configured, for example "00-13-20-F5-F8-7D" then change it to a value that is not duplicated in another NIC on the network or out of the allowed range. To determine the allowed range of MAC addresses: 1. On the virtual machine, open an elevated Command Prompt window, click Start 2. On the Start menu, point to All Programs, click Accessories, right-click Command Prompt, and then click Run as administrator. 3. On the command line type: regedit.exe 4. Open the virtual machine registry and view the following keys: HK_LOCAL_MACHINE\Software\Microsoft\WindowsNT\CurrentVersion\Virtualization\MinimumMacAddress HK_LOCAL_MACHINE\Software\Microsoft\WindowsNT\CurrentVersion\Virtualization\MaximumMacAddress Caution Incorrectly editing the registry might severely damage your system. Before making changes to the registry, you should back up any valued data. Verify The virtual machine starts and runs network operations without any problems. |
| Reference Links | Event ID 12561 from Microsoft-Windows-Hyper-V-VStack-SynthNic |
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