vSAN Errors - "vSAN cluster partition" "vSAN: Basic Connectivity Check" noticed intermittently on the vSAN cluster.

Products

• VMware vSAN

Issue/Introduction

Symptoms:

• The vSAN cluster intermittently enters and resolves the vSAN partition state without manual intervention. During the partitioned state, some ESXi hosts lose the ability to ping other ESXi hosts in the cluster.
• There are no issues identified on the vSAN VMkernel adapters or on the upstream network switches.

Environment

VMWare vSAN 7.x

VMWare vSAN 8.x

VMWare vSAN 9.x

Cause

The IP address assigned to the vSAN VMkernel adapter was also used for VMs in the same cluster, causing IP address duplication. This causes instability in the vSAN cluster, including an intermittent partition state, because it leads to network communication conflicts and routing confusion.

Resolution

The resolution is to stop the IP address duplication.

The user must ensure that the IP address assigned to every vSAN VMkernel adapter is unique across the entire network and is not used by any VM or other device.

The user has two primary options to achieve this:

1. Fix the VM IP Address: Reconfigure the Virtual Machines (VMs) that are using the duplicated IP address to use a unique, available VM IP address. (Recommended, as it's typically less disruptive.)

2. Re-IP the vSAN VMkernel Adapter: Change the IP address of the vSAN VMkernel adapter on the affected ESXi host(s) to a unique, unused IP address. User can reference the KB (How to Non-Disruptively Change the VLAN/IP for vSAN VMk in a Production Environment) to change the vSAN vmkernel IP in a production environment.