Warning: "Network used as backing for overlay network cannot be extended" during HCX Network Extension

Products

• VMware Cloud on AWS
• VMware HCX
• VMware NSX

Issue/Introduction

When configuring a Network Extension for NSX Segment on source in VMware HCX, the network appears twice in the "Extend Networks" interface:

1. As an eligible NSX Segment.
2. As an ineligible Distributed Virtual Port Group (DVPG).

The Source Network displays the following warning message: "Network used as backing for overlay network cannot be extended."

 

Cause

This is expected behavior when extending NSX Segment. When an NSX Segment is created, a corresponding Distributed Virtual Port Group is automatically generated on the backing vSphere Distributed Switch to handle host-level networking. 

During the Network Extension workflow, HCX queries both the vCenter Server inventory (discovering the DVPG) and the NSX Manager inventory (discovering the Segment). HCX structurally restricts the extension of the vSphere backing construct for an NSX overlay network, flagging the DVPG as ineligible.

Resolution

If you are planning to extend an existing NSX Segment using HCX, the logical segment must be selected for extension rather than the underlying vSphere backing port group.

Additional Information

Overlay Network failed to extended with the error "Network used as backing for overlay network cannot be extended"