Receiving alerts in hcx "HCX Interconnect Underlay triggering PMTU Collection failed for the appliance # on serviceMesh : #."

Products

• VMware HCX

Issue/Introduction

HCX Manager intermittently fails to trigger PMTU collection on an Interconnect (IX) appliance. PMTU collection  trigger is failing due to task ongoing on one specific IP, which belongs to IX appliance. The following event is observed in HCX manager /common/logs/admin/app.log

<timestamps> UTC [InterconnectService_SvcThread-42186, IX , TxId: ########-####-####-####-############] ERROR c.v.v.h.s.i.u.PmtuCollectionJob- Failed to trigger PMTU test {}
java.lang.Exception: Another test ongoing for uplink on appliance IP ##.##.##.## with request {"tests":[{"localAddress":"##.##.##.##","remoteAddress":"##.##.##.##"}]} response {"responseCode":429,"responseBody":{"error":"Another testing is ongoing."}}. Error: Another testing is ongoing.

 

The IX appliance reports that the PMTU test is already running locally in /var/log/messages:

<134>1 2026-01-05T03:47:56+00:00 ###-hcx-servicemesh-IX-I1 cgw 1681 - - [Info-restServer] : HandleStartUcPmtu: POST /uc/ondemand/start_pmtu
<134>1 2026-01-05T03:47:56+00:00 ###-hcx-servicemesh-IX-I1 cgw 1681 - - [Info-restServer] : StartUcPmtu(): {"tests":[{"localAddress":"##.##.##.##","remoteAddress":""##.##.##.##"}]}
<133>1 2026-01-05T03:47:56+00:00 ###-hcx-servicemesh-IX-I1 cgw 1681 - - [Notice-restServer] : StartUcPmtu(): test is already running locally

Environment

VMware HCX 

Resolution

If you believe you have encountered this issue, please open a support case with Broadcom Support and refer to this KB article.

For more information, see Creating and managing Broadcom support cases.