Error: Virtual machines lose network connectivity after vMotion migration on ESXi 8.0U3

Products

• VMware vSphere ESXi

Issue/Introduction

Virtual machines (VMs) migrated to a specific ESXi 8.0U3 host in a cluster experience immediate or intermittent network connectivity loss. This issue is often associated with high Receive Overrun (RX OVER) errors on the physical network adapters of the destination host.

Symptoms

• VMs lose network access (ping/application timeouts) immediately after a vMotion migration.
• The issue is isolated to a specific destination host.
• ESXi physical NIC statistics show a high number of Receive over errors.
• Host logs may contain hardware-level reset events (e.g., FCPU reset/Fault F2085 on Cisco adapters).
• Moving the VM back to the original source host restores connectivity.

Environment

• VMware ESXi 8.0U3

Cause

A hardware-level failure or firmware crash on the destination host's Network Interface Card (NIC) causes the adapter to stop processing incoming traffic or fail to notify the physical switch of the VM's new location (RARP/Notify Switches failure). High Receive over errors (RX OVER) confirm the hardware buffer is overflowing because the adapter cannot process packets at the required rate.

Resolution

1. Verify NIC Statistics: Log in to the ESXi host via SSH and run the following command to identify if any physical NICs are reporting errors: esxcli network nic stats get -n vmnic#

2. Check for Overrun Errors: Review the output for Receive over errors. If this counter is incrementing rapidly, the hardware is dropping packets before they reach the ESXi kernel.

3. Monitor Live Statistics: Use the watch command to see if errors increase during a vMotion test: watch esxcli network nic stats get -n vmnic#

4. Review Hardware Logs: Check the hardware vendor’s management console (e.g., Cisco UCS Manager SEL logs) for adapter processor crashes or reset events (e.g., Fault F2085).

5. Update Driver and Firmware: Verify the NIC driver and firmware are on the recommended versions according to the VMware Compatibility Guide.

6. Engage Hardware Vendor: If the NIC driver/firmware is current and Receive over errors continue to persist, engage the hardware vendor to replace the physical network adapter.