Hello Bechir
Welcome to Microsoft Q&A Platform, thanks for posting your query here.
NSX-T Overlay and NSX-T VLAN networks can be extended. These extensions are always created as NSX Overlay networks at the destination. HCX network extension is always to NSX Overlay networks. Pre-created segments in the vSphere Distributed Switch, CVDS, or VLAN transport zone, cannot be used as a destination.
Please refer to below article:
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