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Hyper V Network Trunking

Alan Shoop 0 Reputation points
2026-02-26T19:03:52.6533333+00:00

We have had a brand new HyperV solution installed.
With the way that networking has been configured, I cannot create a trunk port so that a VM can receive tagged packets from multiple VLANs.
The "Trunk Mode" selection is greyed out.
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If I try to cerate a new VLAN based Independent Logical Network, I get this error:
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Do I need to completely delete/destroy my existing Logical Network in order to create a new one of this type?

Moved from: System Center Virtual Machine Manager

Windows for business | Windows Server | Storage high availability | Virtualization and Hyper-V
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  1. Quinnie Quoc 9,595 Reputation points Independent Advisor
    2026-03-03T08:35:00.44+00:00

    Dear Alan Shoop,

    Thank you for sharing the details regarding the new Hyper-V solution and the networking configuration challenges. The Trunk Mode option is only available when the VM network is associated with a Logical Network that has been configured as a VLAN-based Independent Network. The error message you encountered indicates that the subnet being assigned overlaps with an existing subnet, which prevents creation of a new VLAN-based Independent Logical Network. To resolve this, a non-overlapping subnet must be specified. It is not necessary to delete the existing Logical Network unless the current design prevents assigning unique subnets. Adjusting the IP address space or creating a new Logical Network with distinct subnets will allow Trunk Mode to be enabled.

    If this answer resolves your concern, please click Accept the answer so that confirmation is received.

    Best regards,

    QQ.

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  2. Nam Bui (WICLOUD CORPORATION) 1,115 Reputation points Microsoft External Staff Moderator
    2026-03-03T08:06:24.37+00:00

    Hi Alan ,

    Thank you for your question. 

    This behavior is expected in System Center Virtual Machine Manager (SCVMM). 

    Why “Trunk Mode” is greyed out 

    In SCVMM, Trunk Mode on a VM network adapter is only available when the VM network is backed by a VLAN‑based Independent Logical Network.  In your current configuration, the VM network is associated with a Connected (non‑independent) Logical Network, so the Trunk Mode option is disabled by design. 

    About the subnet overlap error (ID: 13638) 

    The error message indicating that subnet 10.10.0.0/24 overlaps with an existing subnet means that this subnet already exists somewhere in SCVMM.  SCVMM enforces global subnet uniqueness across all Logical Networks, not just within a single Logical Network. 

    Do you need to delete the existing Logical Network? 

    If you want to enable Trunk Mode through the SCVMM UI, then yes—the supported approach is to: 

    Migrate or remove dependent VM networks 

    Delete the existing Logical Network 

    Recreate it as a VLAN‑based Independent Logical Network, ensuring that all defined subnets do not overlap 

    Once this is done, Trunk Mode will be available for VM network adapters. 

    Alternative option 

    If redesigning the Logical Network is not feasible, you can configure VLAN trunking directly on the VM network adapter using Hyper‑V PowerShell. This approach works at the Hyper‑V level but will not be fully manageable through the SCVMM UI. 

     If this explanation resolves your question, please mark it as Accepted Answer so it can help others with the same issue. 

    Best regards, 
    Titus Bui

     

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