Intermittent ESXi Management Network Failover with Cisco Fabric Interconnects on vSphere 8.0 Update 3

Products

• VMware vSphere ESXi

Issue/Introduction

Customers running VMware ESXi 8.0 Update 3 with Cisco Fabric Interconnect–based networking may observe intermittent management network connectivity changes. These events typically present as temporary uplink failures followed by automatic failover, without a complete loss of host connectivity.

 

This article describes the observed behavior, likely cause, and recommended validation steps.

Environment

• VMware ESXi 8.0 Update 3
• vCenter Server 8.0 Update 3
• Cisco Fabric Interconnect–based networking
• Redundant physical uplinks configured for ESXi management networking

 

Cause

A physical network interface on the ESXi host temporarily transitions to a down state, triggering a management network failover to an alternate uplink.

 

Resolution

No immediate ESXi-side remediation is required if failover completes successfully and host connectivity remains intact.

 

To help prevent recurrence, validate the upstream physical network path associated with the affected vmnic, including:

• Cisco Fabric Interconnect switch port configuration and health
• Cabling integrity
• Physical NIC health on the ESXi host
• Fabric Interconnect port logs and error counters

 

Additional Information

If you are experiencing similar management network failover events, reviewing ESXi host logs can help confirm whether the behavior is related to upstream network conditions.

 

In cases reviewed, ESXi hosts logged vmnic link state changes without evidence of host-side failures such as NIC driver crashes or hardware resets. The ESXi networking stack continued to function as designed by failing over to an available uplink and maintaining management connectivity.

 

To further investigate, review the following ESXi log files around the time of the event:

• vmkernel.log – vmnic link up/down events, driver resets, or hardware-level network errors
• vobd.log – VMkernel Observations related to network connectivity warnings
• net.log (on newer ESXi versions) – Detailed networking stack and uplink events
• syslog.log – Forwarded or summarized network-related messages depending on configuration

 

If vmnic link state changes are observed without corresponding ESXi driver or hardware errors, this typically indicates an upstream physical network condition rather than an ESXi host issue. In such cases, validating the switch ports, cabling, and Fabric Interconnect configuration associated with the affected uplink is recommended.