Duplicated virtual MAC of vmnic from different ESXi

Products

• VMware vSphere ESXi 8.0

Issue/Introduction

Symptom

• TOR physical switch found duplicated MAC 00:50:56:xx:xx:xx from different ESXi
• These duplicated MAC are vmnic virtual MAC, the similar output are below

[root@esxi:~]  netdbg vswitch instance list
  Client                         PortID          DVPortID                             MAC                  Uplink          VID              VNI
  Shadow of vmnicx               xxxxxx                                            00:50:56:xx:xx:xx       n/a             N/A              N/A

 

 

Environment

VMware vSphere ESXi 8

Cause

According to the VMware OUI allocation scheme, a MAC address has the format 00:50:56:XX:YY:ZZ where 00:50:56 represents the VMware OUI.

Each vmnic has one virtual MAC and it is generated automatically by ESXi. While very rarely there is duplicated virtual MAC for vmnic across ESXi hosts in the environment.

Resolution

Reinstall ESXi to re-generate new virtual MAC