ESXi Host Management Network Isolation During Uplink Failover

Products

• VMware vSphere ESXi

Issue/Introduction

ESXi hosts may enter a Not Responding state in vCenter Server during physical uplink failover events.
This behavior occurs when the Management VMkernel interface (vmk0) inherits the burned-in physical MAC address of an uplink NIC.
When the active uplink fails and traffic fails over to a secondary physical NIC, the upstream physical switch may block the management traffic due to a perceived MAC address conflict or port-security violation.

Environment

VMware vSphere ESXi

Cause

During the initial installation of ESXi, the Management VMkernel interface (vmk0) may inherit the physical hardware MAC address of the first detected NIC (vmnic).
When an uplink failure triggers a failover to a different physical NIC, the ESXi host emits Reverse ARP (RARP) packets using the hardware MAC address of the original physical NIC.
Upstream physical switches may block traffic originating from a hardware MAC address that is currently being seen on a switch port different from the one originally associated with that MAC, resulting in a loss of host connectivity.

Resolution

To resolve this issue, remove and recreate the management VMkernel interface.
This process forces the ESXi host to assign a dynamic VMware OUI-based MAC address (beginning with 00:50:56), decoupling the VMkernel interface from the physical hardware MAC address of the NIC.

Prerequisites:

• Access to the ESXi host via ILO/Direct Console User Interface (DCUI).
• Verification of the current Management network configuration (IP address, subnet mask, and port group name).

Steps:

1. Log in to the ESXi host shell as the root user.
2. List the current VMkernel interface configuration to identify the port group associated with the management network:

   esxcfg-vmknic -l

3. Remove the existing Management VMkernel interface:

   esxcli network ip interface remove --interface-name=vmk0

4. Recreate the Management VMkernel interface to trigger the assignment of a dynamic VMware MAC address:

   esxcli network ip interface add --interface-name=vmk0 --portgroup-name="Management Network"
   esxcli network ip interface ipv4 set --interface-name=vmk0 --ipv4=<your_ip> --netmask=<your_subnet> --type=static
   

5. Verify that the new MAC address for vmk0 now begins with 00:50:56:

   esxcfg-vmknic -l

Additional Information

• If connectivity issues persist, provide the specific incident timeframe (start and end time of the disconnection) to the network administration team to inspect switch logs on the switchport connected to the secondary physical NIC.
• For further technical details on addressing inherited MAC addresses on ESXi management interfaces, refer to KB 318928.
• If the issue is not resolved, collect a support bundle and contact Broadcom Support. Refer to Contact Broadcom Support for assistance.