Frequent path redundancy degraded on Cisco UCS hosts with "tport is NULL" warnings

Products

• VMware vSphere ESXi

Issue/Introduction

Symptoms:

• ESXi hosts enter a non-responsive state, and Virtual Machines (VMs) appear disconnected in the vCenter UI.

• esxcli commands fail to execute or hang on affected hosts.

• The vCenter UI displays warnings: Path redundancy to storage device naa.#### degraded.

• From ESXi, var/log/vobd.log there is an event for "Path state changes indicating storage connectivity issues"

  2025-05-31T06:03:30.536Z: [scsiCorrelator] 12246182344412us: [vob.scsi.scsipath.pathstate.dead] scsiPath vmhba2:C0:T6:L1 changed state from on
  2025-05-31T06:03:30.538Z: [scsiCorrelator] 12246182344611us: [vob.scsi.scsipath.remove] Remove path: vmhba2:C0:T6:L1
  2025-05-31T06:03:30.538Z: [scsiCorrelator] 12246182345421us: [vob.scsi.scsipath.pathstate.dead] scsiPath vmhba2:C0:T6:L2 changed state from on

• In var/run/log/vmkernel.log, the nfnic driver reports target port unavailability
  

  nfnic: <1>: INFO: fnic_queuecommand: 731: returning IO as lun is inactive or tport is NULL. driverIO:0

Environment

VMware vSphere ESXi 7.x
VMware vSphere ESXi 8.x 
Cisco nfnic driver

Cause

The message "returning IO as LUN is inactive or tport is NULL" indicates the ESXi host is unable to process I/O requests because the SAN target port is unavailable or the LUN is administratively inactive.

Resolution

1. Verify Fabric Health: Check Cisco UCS Manager for I/O Module or Fabric Interconnect (FI) alerts.
2. Review Storage Controller Logs: Engage the storage vendor to investigate why target ports are intermittently unavailable.
3. Firmware Alignment: Ensure the Cisco UCS server BIOS and VIC firmware are updated to the latest supported versions on the.
   VMware Compatibility Guide

If the issue persists after storage and fabric remediation, see Contact Support. Scroll to the bottom of the page and click on your respective region.