Manual time sync on ESXi host using ntp udate fails with: no server suitable for synchronization found.

Products

• VMware vSphere ESXi

Issue/Introduction

ESXi host is unable to synchronize time with internal Linux-based NTP servers.

 

Environment

VMware ESXi 8.0.x

Cause

The ESXi host was sending NTP requests but not receiving any responses due to a malfunctioning chronyd service on the NTP server side.

ntpq -p output showed:

reach = 000 
stratum = 16 
refid = .INIT. 
condition = reject

Resolution

Run through the following to verify the configuration and point on contention:

• Check on ESXi Host:

  • NTP client (ntpd) was enabled.

  • Firewall rule ntpClient was active and allowed outbound NTP traffic.

• Action need by NTP/Network Team

  • Verify there were no firewall blocks affecting inbound NTP responses.

  • Investigate the NTP servers and ensure the chronyd service is functioning as expected.

  • Reconfig and restart the chronyd service.

  • Verified that the NTP server was reachable from the ESXi host.

 

Additional Information

Validate the below KB for know issue:

Time Synchronization Services test warning "Configuration is not working normally".

To troubleshoot this NTP issue follow KB:

Troubleshooting NTP on ESX and ESXi 6.x / 7.x / 8.x