Duplicate VMkernel MAC Addresses Detected Across ESXi Hosts in vCenter Server.

Products

• VMware vSphere ESXi

Issue/Introduction

• Duplicate VMkernel MAC addresses have been detected across multiple ESXi hosts within the same vCenter Server inventory.
• This issue primarily affects TEP interfaces (such as vmk10, vmk11, etc.) that are automatically created during NSX installation on each host. However, though rarely seen, issue has been reported on other vmk interfaces too such as vMotion, vSAN, etc.

Environment

VMware vSphere ESXi

Cause

• Currently, vCenter Server does not provide MAC address collision detection for VMkernel interfaces, nor does it implement a MAC address pool for these interfaces. As a result, environments operating at larger scales may encounter MAC address conflicts.
• ESXi hosts ensure the uniqueness of VMkernel MAC addresses only within the local host if the address is generated by the host. Since ESXi hosts are not aware of MAC addresses assigned to VMkernel interfaces on other hosts managed by the same vCenter Server, duplicate MAC addresses can occur across hosts.

Resolution

• For duplicate MAC on the vMotion vmk interface, place the host in maintenance mode, delete the interface and recreate it.
• For duplicate MAC on the vSAN vmk interface, place the host in maintenance mode (choose the migration option "Ensure Accessibility"), delete the interface and recreate it within 60mins of placing the host in MM (post 60mins in maintenance mode, it may start a resync).
• For duplicate MAC on the ESXi vtep interfaces, place the host in maintenance mode, uninstall NSX from the ESXi - Troubleshooting NSX Uninstall Process and reprepare it for NSX.