vSAN ESA Upgrade Blocked Due to Network Health Check Failures

Products

• VMware vSAN

Issue/Introduction

During an upgrade of a VMware vSAN ESA cluster to vSphere 8.0 U3h, the remediation process may fail with multiple vSAN health check errors, preventing hosts from being upgraded.

Remediation of cluster failed Health Check for 'vSANCluster' failed vSAN health test 'vSAN cluster partition' reported an issue for cluster 'vSANCluster'. Check the vSAN health.
vSAN health test 'vSAN: Basic (unicast) connectivity check' reported an issue for cluster 'mrsac-clstr'. Check the vSAN health.vSAN health test 'vSAN: MTU check (ping with large packet size)'
reported an issue for cluster 'vSANCluster'. Check the vSAN health. vSAN health test 'vMotion: Basic (unicast) connectivity check' reported an issue for cluster 'vSANCluster'. Check the vSAN health.
vSAN health test 'vMotion: MTU check (ping with large packet size)' reported an issue for cluster 'vSANCluster'. Check the vSAN health. <host ip> - Skipped remediation for this host
Host '<host ip>' was not processed, the reason: 'Health Check for 'vSANCluster' failed' 1Host skipped

Symptoms

• A Skyline Health Alert was triggered: "URGENT: IMMEDIATE ACTION REQUIRED - vSAN ESA UPGRADE"

• Remediation of the cluster fails with multiple connectivity errors:
  • vSAN: Basic (unicast) connectivity check
  • vSAN: MTU check (ping with large packet size)
  • vMotion: Basic (unicast) connectivity check
  • vSAN cluster partition

Environment

VMware vSAN 8.x

vSAN ESA 

Cause

The issue is typically caused by manual network reconfiguration on a host during the upgrade window (e.g., removing/re-adding a host to vCenter or creating standard vSwitches). This results in:

• Improper NIC Assignment: Physical NICs not being correctly reattached to vSAN/vMotion uplinks.
• Network Inconsistency: Disruption of communication between the upgraded host and the rest of the cluster.
• Unsupported State: The cluster enters a mixed-version state with broken networking, which prevents the remaining hosts from remediating.

Resolution

To resolve this and resume the upgrade, network consistency must be restored to the affected host(s):

1. Verify NIC Mapping: Ensure physical NICs are assigned to the correct vSAN and vMotion uplinks according to your cluster design.

2. Validate VMkernel Binding: Confirm that the VMkernel interfaces are properly bound to the designated uplinks.

3. Check MTU Consistency: Ensure the MTU settings (e.g., 9000 for Jumbo Frames) are consistent across all hosts and physical switches.

4. Confirm Connectivity: Run a manual ping test with large packet sizes between hosts to ensure the vSAN/vMotion network is stable.

5. Resume Upgrade: Once all health checks pass or the "vSAN cluster partition" error is cleared, proceed with the remediation of the remaining hosts.

Additional Information

 

• Avoid making manual network changes during upgrade operations

• Ensure cluster networking is validated prior to initiating vSAN ESA upgrades

• Maintain consistent network configuration across all hosts to prevent upgrade disruption