Network adapter (vmnic) is down or fails with a Failed Criteria Code in VMware vSphere ESXi

Products

• VMware vSphere ESXi

Issue/Introduction

Physical network adapters (vmnics) may report a down state or experience frequent flapping, leading to critical service disruptions. In environments using Cisco UCS hardware, this can manifest as All Paths Down (APD) states for NFS datastores, potentially triggering vSphere High Availability (HA) reboots of ESXi hosts.

Symptoms:

•  NIC adapter alerts in the ESXi or vCenter UI: "Network uplink redundancy degraded" or "Lost Network Redundancy."
•  In /var/run/log/vobd.log, entries similar to: 2026-06-13T03:12:48.002Z In(14) vobd[2097574]: [netCorrelator]: [esx.problem.net.redundancy.lost] Lost uplink redundancy on virtual switch "vSwitch0". Physical NIC vmnic0 is down.
•  Failed criteria code 128 is reported in logs.
•  NFS datastores enter APD state followed by [esx.problem.vmfs.nfs.server.disconnect].
•  ESXi hosts may reboot unexpectedly due to HA events after storage connectivity loss.

Environment

• VMware vSphere ESXi 7.0.x / 8.0.x
• Cisco UCS B-Series / C-Series Servers
• Cisco Native Fibre Channel (nfnic) drivers
• NFS Storage

Cause

This issue occurs when the physical network layer becomes unstable. Frequent flapping (linkstate up/down) is often caused by outdated or incompatible network drivers (e.g., nfnic), firmware mismatches, or hardware faults within the Cisco UCS Fabric Interconnect (FI) domain.

    

Resolution

 

• Verify the current status of the vmnic using the command: esxcli network nic list
• Review /var/run/log/vobd.log for "Failed criteria: 128". This indicates the driver is reporting a link state down.
• Identify the version of the nfnic driver currently in use. Refer to .
• Update the network drivers to the latest certified version. See to retrieve updated drivers.
• If using Cisco UCS, verify the health of the Fabric Interconnects and check for recent subordinate FI reboots.
• Engage your hardware vendor (Cisco) to perform a Root Cause Analysis (RCA) if NIC flapping persists after driver updates.

 

Additional Information

 Refer to for specific stability known issues.
    For more on log collection, see .