HCX fails to extend a pre-created segment on VMware Cloud on AWS
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HCX fails to extend a pre-created segment on VMware Cloud on AWS

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Article ID: 394772

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Updated On: 04-21-2025

Products

VMware HCX VMware Cloud on AWS

Issue/Introduction

  • An additional Tier-1 gateway was created in NSX on VMware Cloud on AWS.
  • On this Tier-1 gateway, a segment with the subnet you intend to extend from the on-premises environment was pre-created.
  • From the HCX Connector (source), HCX correctly detects that the same subnet exists during the validation process.
  • You selected the "Override Subnet" option, but the HCX network extension workflow fails, with the following error observed in /common/logs/admin/app.log:
    <timestamps> UTC [NetworkStretchService_SvcThread-968, j: ########, s: ########, , TxId: ########-####-####-####-###########] ERROR c.v.v.h.n.i.AbstractJobInt- NetworkStretchJobs workflow prepareCloudNetwork failed. Error: Error creating NSX-T Segment. Address ###.###.###.##/## overlaps with Segment path=[/infra/segments/<segment-name>] that has subnet ###.###.###.###/##.
  • This error is also visible in the HCX UI under SystemAdministrationActivity Logs, similar to the screenshot below:

Environment

HCX
VMware Cloud on AWS

Cause

The issue occurs due to the difference in segment creation paths between VMC and Non-VMC deployments:

   1. In VMC deployments, the expected segment path is:
      infra/tier-1s/<tier-1_id>/segments/<segment_id>

   2. In Non-VMC deployments, the segment path used is:
      infra/segments/<segment_id>

Because of this distinction, deployments using the non-VMC path format in a VMC environment fail. Specifically, in VMC, when a new Tier-1 (other than CGW or MGW) is created followed by addition of segment, the UI/API defaults to using the path /infra/segments/. However, per VMC architecture guidelines, segments must be created under: infra/tier-1s/<tier-1_id>/segments/.

Resolution

This is a condition that may occur in a VMware HCX environment on VMware Cloud on AWS.

Workaround:

Option 1: If you need to use a pre-created segment in NSX, you can use the default Tier-1 (CGW - Compute Gateway).
Option 2: If you need to extend to a dedicated Tier-1, pre-created segments are currently not supported. However, you can still extend the network if the segment is not pre-created.

Additional Information

Note that this specific issue only affects VMC environments using a new Tier-1 and pre-created networks. If you are experiencing a similar error message, refer to the KB: HCX - Error while extending pre-created segments "Error creating NSX-T Segment. Address, overlaps with Segment path"