Virtual machines appear inaccessible and ESXi hosts show Not Responding after VLAN change

Products

• VMware vSAN

Issue/Introduction

• Virtual machines (VMs) are in an inaccessible state in vCenter Server.
• Multiple ESXi hosts show as Not Responding or Disconnected in the vSphere Client.
• Running esxcli vsan cluster get on ESXi hosts shows a Sub-Cluster Member Count of 1 or a reduced number of members.
• Pings between vSAN VMkernel interfaces (vmk) fail.

Environment

• VMware vSphere 7.x
• VMware vSphere 8.x
• VMware vSAN 7.x
• VMware vSAN 8.x

Cause

This issue occurs when a configuration change or rollback on the vSphere Distributed Switch (vDS) results in a network partition or an incorrect VLAN tagging at the physical hardware level (e.g., iLO/Integrated Management Module settings for physical NICs) prevents the vSAN management traffic from communicating across the hosts after a switch-side rollback.

Resolution

To resolve this issue, you must verify and correct the VLAN configuration at both the physical switch and the host hardware level.

1. Establish a console connection to the affected ESXi hosts via iLO, iDRAC, or local CLI.
2. Verify the current vSAN network configuration: esxcli vsan network list
3. Test connectivity between host VMkernel interfaces using vmkping: vmkping -I vmk#### ####.####.####.#### (Note: Replace #### with the appropriate vmk interface and peer IP address.)
4. Check the physical NIC/LOM settings in the host management interface (e.g., HP iLO). Ensure that the VLAN ID assigned to the physical adapter matches the expected vSAN/Management VLAN tag configured on the physical switch ports.