Microsoft Failover Cluster Witness loss and vSphere HA Unreachable status due to network packet corruption

Products

• VMware vSphere ESXi

Issue/Introduction

Microsoft Failover Clusters lose connectivity to the File Share Witness. Simultaneously, ESXi hosts transition to a vSphere HA Unreachable state in vCenter. While the virtual machines remain powered on, they lose application-level cluster synchronization.

You find the following entries in your log files during the incident window:

• Fdm (HA) Logs: SSL_connect error with Connection reset by peer. This indicates the HA agent on host #### lost communication with vCenter.

• clusterAgent Logs: Failed to SSL handshake; ... e: 336151151(ssl/record/methods:version too low).

• vpxd Logs: Host transitions to Agent Unreachable and vCenter cancels HA monitoring for the node.

• vmkernel Logs: The infravisor service triggers the deletion of vCLS-#### pods as a consequence of a host connection flap.

Environment

vCenter 8.0x
vSphere 8.0x

Cause

The cause is a transient management network flap at the physical link level. This instability results in packet truncation and corruption, which disrupts both the ESXi management plane (FDM/VPXA) and the VM Network traffic used by Microsoft Failover Cluster heartbeats.

The specific error code : Failed to SSL handshake; ... e:336151151(ssl/record/methods:version too low) is a indicator of malformed or truncated packets occurring during an SSL handshake. This is typically caused by network hardware instability rather than a software defect. Because the disruption is brief (often less than 30 seconds), it does not trigger a full vSphere HA isolation response, leaving VMs powered on but disconnected at the network layer.

Resolution

1. Conduct a Physical Infrastructure Audit
   Inspect the physical switches connected to your ESXi management and VM network interfaces. Look for CRC errors, port flaps, or MTU mismatches that correlate with the timing of the disconnects.

2. Align Firmware and Drivers
   Update the BIOS and Fiber Channel (FC) HBA drivers for your hosts (e.g., Dell PowerEdge ####) to the latest versions certified on the VMware Compatibility Guide. Current drivers ensure stable I/O handling and prevent timeouts during transient network events.

3. Resynchronize HA State
   In the vSphere Client, right-click each affected host and select Reconfigure for vSphere HA. This forces a full state synchronization of the Fault Domain Manager (FDM) agents and clears residual metadata corruption caused by the network flap.