VCHA Failover fails if Active VCenter VM has NIC MAC Address set to Manual.

Products

• VMware vCenter Server

Issue/Introduction

Avoid setting the MAC address assignment mode of Network adapter 1 and Network adapter 2 in a vCenter High Availability (VCHA) configuration to Manual.
This configuration can lead to failover issues and network connectivity problems.

Symptoms

• After a VCHA failover, ESXi hosts managing the vCenter VM become unreachable.

• Hosts appear as disconnected in the vSphere Client.

• vCenter Server Appliance logs indicate dropped packets on NIC1 (eth0) or NIC2 (eth1).

Environment

VMware vCenter Server 8.0.x
VMware vCenter Server 6.5.x
VMware vCenter Server 6.7.x
VMware vCenter Server 7.0.0

Cause

The Active vCenter VM has one or more virtual NICs (NIC1 or NIC2) configured with Manual MAC address assignment. This results in MAC address duplication across the Active, Passive, and Witness nodes in the VCHA setup, causing network instability and packet loss during failover.

Resolution

VMware is aware of this issue and is actively working to resolve it in a future product release.

Workaround

1. To prevent this issue, do not configure virtual NICs with a manual MAC address in a VCHA setup. Instead, follow these steps:

   1. Place the VCHA cluster into Maintenance Mode.

   2. Note the ESXi host each VCHA node (Active, Passive, and Witness) is currently running on.

   3. Power off the node that has a MAC address configured as "Manual".

   4. Edit the VM settings for each VCHA node (Active, Passive, and Witness):

      • Navigate to the Network Adapter settings for NIC1 and NIC2.

      • Check the MAC Address configuration.

      • Ensure the setting is not set to "Manual".

      • Change the MAC Address setting to "Automatic".