Error when trying to extend a network on HCX "Failed to get a free VNic for Network Extension"

Products

• VMware HCX

Issue/Introduction

• When trying to redeploy network extension appliance, the following error is observed.
  
  
  
• Unable to perform additional network extensions even when the NE shows 7/8 networks extended. The following error can be seen on source HCX-MGR app.log (/common/logs/admin).
  

  • 2025-03-11 20:39:42.631 UTC [NetworkStretchService_SvcThread-90, j: 3c689dce, s: ec5e35ce, , TxId: ########-####-####-####-3ce6e411e307] ERROR c.v.v.h.n.i.AbstractJobInt- NetworkStretchJobs workflow AllocateBridgeVnicsJobInt failed. Error: Failed to get a free VNic for Network Extension.

 

Environment

HCX

Cause

NE appliance could not be redeployed due to a stale network segment present in HCX DB. This stale NSX segment is no longer present in NSX Manager.

These stale segments can be caused by:

• User manually removing a segment from NSX-T manager that is actively in use by HCX.
• Manually altering HCX appliance vNICs in vCenter UI directly. 

Resolution

Perform a resync of the affected service-mesh. If a resync does not allow for appliance redeployment, please collect and provide the following details when opening a Broadcom SR. 

• Screenshot of error message.
• Network name being extended.
• Appliance name being redeployed and service-mesh the NE belongs to. 
• Source/Destination HCX-MGR log bundles with DB dumps included.