Windows Hyper-V Virtual Switch Loses Network Connectivity

Use a host-first isolation path and match symptoms to the known Hyper-V networking failure patterns:

1. Check whether the virtual switch is still bound to the physical adapter.
   • If creating or re-creating a vSwitch fails with errors such as “already bound to another virtual network” or “Failed while adding virtual Ethernet switch connections”, inspect the Hyper-V switch protocol binding on the adapter:

      Get-NetAdapterBinding -ComponentID "vms_pp"
   

   • If the affected adapter still shows Enabled = True, remove that binding:

      Disable-NetAdapterBinding -Name "<Adapter Name>" -ComponentID "vms_pp"
   

   • Run Get-NetAdapterBinding -ComponentID "vms_pp" again and confirm Enabled is False.
   • On upgraded Windows 10 systems, deleting a vSwitch may leave stale objects behind even when the switch no longer appears in Virtual Switch Manager. In that case, the documented Easy fix can remove the stale configuration. Risk: network connectivity is lost when the wizard finishes, a manual restart is required, Wi‑Fi networks must be reconnected manually, and the vSwitch must be created again after restart.
2. Check whether the issue is VMQ on the host NIC.
   • If VMs randomly lose connectivity and a host reboot restores all VMs, this matches the known VMQ issue on some adapters.
   • For Broadcom NetXtreme 1‑gigabit adapters on Windows Server 2012/2012 R2, update to b57nd60a.sys version 16.8 or newer. If that is not possible, disable VMQ on each affected adapter:

      Set-NetAdapterVmq -Name "NIC 1" -Enabled $False
      Set-NetAdapterVmq -Name "NIC 2" -Enabled $False
   

   • Verify with:

      Get-NetAdapterVmq
   

   • For host NIC VMQ-related loss on other adapters, the documented resolution uses registry changes for RSS/VMQ behavior. Risk: incorrect registry edits can cause serious problems; back up the registry first and reboot the host after changes.
3. Check VLAN and forwarding-extension combinations.
   • If connectivity loss started after enabling VLAN tagging together with a third-party forwarding extension and Hyper-V Network Virtualization (HNV) on Windows Server 2012 R2 managed by VMM, that combination is a documented cause of lost virtual network connectivity.
   • In that scenario, treat VLAN tagging plus the forwarding extension as the likely trigger.
4. Check whether teaming is involved.
   • If the host uses NIC Teaming, treat it as a possible cause. Microsoft support policy states NIC Teaming is vendor technology, and troubleshooting may require temporarily disabling or removing the teaming software.
   • Common symptoms of improperly configured teaming include intermittent VM network loss, loss after live migration, and VMSMP Event ID 28 in the System log.
   • If using Switch Embedded Teaming (SET), the accepted guidance in the provided Q&A is that SET supports only Switch Independent mode. Physical switch ports connected to SET members should be configured as independent ports, not as a static LAG/LACP port channel. If switch logs show port state changes without physical link loss, correct the upstream switch configuration first.
5. Use symptom mapping to narrow the cause.
   • Cannot create/re-create vSwitch → likely stale vms_pp binding or stale switch objects.
   • All VMs recover only after host reboot → likely host NIC/VMQ issue.
   • Connectivity loss begins after VLAN tagging + third-party forwarding extension + HNV → likely VLAN/extension interaction.
   • Intermittent loss, live migration issues, VMSMP Event ID 28, or switch port flaps with teamed adapters → likely teaming or switch configuration mismatch.

This sequence separates binding problems, VLAN-related breakage, teaming misconfiguration, and host NIC networking issues with the least ambiguity.

• Creating V-switches within the hyper-V environment fails
• Can't create a Hyper-V virtual switch on 64-bit versions of Windows 10
• Virtual machines lose network connectivity when you use Broadcom NetXtreme 1-gigabit network adapters
• Network connectivity is lost on Hyper-V VMs if VMQ feature is enabled on HOST network cards
• VLAN tagging breaks the VM connection with a third-party forwarding extension and HNV in Windows Server2012 R2 | Microsoft Support
• Microsoft support policy for NIC Teaming with Hyper-V
• My Hyper-V SET team experiences periodic port shutdowns without any physical link failure. Ports shut down on their own. How can I adjust switch and team configurations. Host is on Hyper-V infrastructure. - Microsoft Q&A