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Microsoft: December Windows Server updates break Hyper-V VM creation

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Microsoft claims that Windows Server Updates released on December Patch Tuesday could cause errors in the creation of new Hyper-V virtual machines.

This issue only affects Windows Server/AzStack hosts that are part of SDN-enabled environments managed with System Center Virtual Machine Managers (SCVMM).

Microsoft explains that you might get an error when creating a Network Adapter, also known as a Network Interface Card (or NIC), joined to a VM Network or a Virtual Machine (VM), with a Network Adapter connected to a VM Network.

Existing VMs connected to existing Network Adapters will not experience any problems after this update. Only new Network Adapters that have been installed after this update is applied are affected.

Windows administrators will experience one of these errors on affected systems:

  • New VM creation failed: Creating a VM with Network adapter is not possible.
  • SLB load balancer or SDN-RAS Gateway fails with an ‘EthernetConnection’ error
  • Attaching vNIC failed: Attaching a network adapter to an already existing VM.
  • Warning message in live migration: The Live Migration of Non-Highly Available Virtual Machines finishes with an “EthernetConnection” warning message.

Microsoft stated that Windows Server 2019 should not be affected by this month’s Patch Tuesday update ( , ).






Version VMM






Hyper-V patches with KB5021249/KB5021237






SDN enabled






Impacted





HTMLMM 2019





2012 R2, 2016, 2019 HCI 21H2

















HTML5_ VMM 2019





2012 R2, 2016





Yes





HTML4_ HTML5_ HTML6_ HTML7_ HTML8_ HTML5_






VMM 2019






2019 HCI 21H2






Yes






Yes





HTML4_ VMM 2022





2016 – 2019, 2022 HCI 22H2





HTML4_ HTML5_ HTML4_ HTML5_ HTML4_ HTML5_ HTML5_ HTML6_ HTML7_ HTML8_ HTML5_ HTML8_





HTML3­





VMM2022





2016





Yes





HTML3­






VMM 2022






2020, 2022 HCI 22H2






Yes






Yes

There are workarounds available

Microsoft also offered a solution to the issue for administrators of SCVMM-based SDN deployments.

This requires that you run the following commands from elevated PowerShell windows on SCVMM-managed Hyper-V hosts (immediately after installing KB5021237 or KB5021249 update): 

$lang = (Get-WinSystemLocale).Name C:Windowssystem32wbemmofcomp.exe C:Windowssystem32wbemen-USVfpExt.mfl C:Windowssystem32wbemmofcomp.exe C:Windowssystem32wbemVfpExt.mof

Administrators may also perform this task after the SCVMM Management Server has installed the update. If the host count is large, or if running manual commands would take too much time, the script can be used to bulk deploy the workaround.

Microsoft provides a postinstall script to be used in conjunction with the patching tools for updating the KB5021237 or KB5021249 versions.

The scripts are available for large-scale deployments. For more information on the workaround, see .

Redmond it is working to fix the issue. It will also provide an update in a future version.

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