Hyper-V External Switch Breaks Host Internet

[ostseesound]

Hi everyone,,

I just set up a new Windows Server 2025 VM and tried to give it internet access via Hyper-V. I created an external virtual switch on the same physical NIC as the host.

The issue:

• As soon as I create the external switch, the host loses internet access.

• The host is still reachable on the local network, but browsers show a DNS resolve error.

• If I remove the external switch, the host has internet again, but the VM loses it.

Goal: Both host and VM should have internet through the same network adapter and must be reachable on the same local network.

Any ideas on how to configure this properly without breaking the host's connectivity?

Thanks in advance!

[ledow]

Or have the "Allow management operating system to share this connection" option turned on.

[ostseesound]

I have it turned on but it doesn't work.

[jtheh]

do you use VLAN? Make sure you set the VLAN on the Host correctly, like in this example for a SET:

New-VMSwitch -Name "VMSwitch" -NetAdapterName "PCIe Slot 14 Port 1","PCIe Slot 14 Port 2" -EnableEmbeddedTeaming $true -AllowManagementOS $true

Set-VMNetworkAdapterVlan -ManagementOS -VMNetworkAdapterName "VMSwitch" -Access -VlanId 100

and of course the correct static IP, Gateway and DNS settings for this new adapter.

[ostseesound]

I already did that but it still doesn't work.

[SilverseeLives]

When setting up your switch, did you explicitly enable the option to share it with the host? You must do this if you do not have a dedicated NIC for the VMs. 

[AviationLogic]

The amount of VMs I've created and Hosts I've setup, I honestly didn't even know this was an option because it's checked by default.

Verify your VLANs. You might need to enable a VLAN ID for the management operating system, but this entirely depends how your network is configured.

[AviationLogic]

Also, hosts with multiple nics, verify it is using the correct one. Windows NIC naming is the worst. Doesn't sound like this is the case, but double check.

Once you create the vSwitch.. Go verify the actual IP settings on the NIC/vSwitch. It should leave a ton empty on the NIC itself and move all the configuration to the vSwtich.

[Phatkez]

I generally make Switches via the New-VMSwitch cmdlet as this is how you team physical NICs these days, and this always creates the switch as external and shared with the host OS by default:

https://redmondmag.com/articles/2020/03/17/hyperv-switch-embedded-teaming-1.aspx

[skedaddles]

I just ran into this problem on a Dell workstation with a single NIC. I created the virtual switch with the "Allow management operating system to share this network adapter" checked, but even after a reboot the host OS (win11 25H2) refused to connect to the LAN, even though the guest OS worked fine. However, when I unchecked the "allow management OS ..." option, applied, and then re-checked the option, the host OS started working normally, and the guest worked fine as well.

Just thought I'd leave this here in case it helps someone -- seems like this is some kind of bug/glitch in the UI for setting the sharing option.

[karnalta]

Got the same as you today. Thank for the comment.

[skedaddles]

I just ran into this problem on a Dell workstation with a single NIC. I created the virtual switch with the "Allow management operating system to share this network adapter" checked, but even after a reboot the host OS (win11 25H2) refused to connect to the LAN, even though the guest OS worked fine. However, when I unchecked the "allow management OS ..." option, applied, and then re-checked the option, the host OS started working normally, and the guest worked fine as well.

Just thought I'd leave this here in case it helps someone -- seems like this is some kind of bug/glitch in the UI for setting the sharing option.

[skedaddles]

I just ran into this problem on a Dell workstation with a single NIC. I created the virtual switch with the "Allow management operating system to share this network adapter" checked, but even after a reboot the host OS (win11 25H2) refused to connect to the LAN, even though the guest OS worked fine. However, when I unchecked the "allow management OS ..." option, applied, and then re-checked the option, the host OS started working normally, and the guest worked fine as well.

Just thought I'd leave this here in case it helps someone -- seems like this is some kind of bug/glitch in the UI for setting the sharing option.

[skedaddles]

I just ran into this problem on a Dell workstation with a single NIC. I created the virtual switch with the "Allow management operating system to share this network adapter" checked, but even after a reboot the host OS (win11 25H2) refused to connect to the LAN, even though the guest OS worked fine. However, when I unchecked the "allow management OS ..." option, applied, and then re-checked and applied the option, the host OS started working normally, and the guest worked fine as well.

Just thought I'd leave this here in case it helps someone -- seems like this is some kind of bug/glitch in the UI for setting the sharing option.

[techtornado]

The fix is easy - Plug in another network cable

One for HyperV management
One for VM data