NTP Service Test Failure in vSphere Client Following ESXi Host Maintenance
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NTP Service Test Failure in vSphere Client Following ESXi Host Maintenance

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Article ID: 452978

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Updated On:

Products

VMware vSphere ESXi VMware vCenter Server

Issue/Introduction

In the vSphere Client, administrators may encounter a failure when performing a "Service Test" for the Network Time Protocol (NTP) daemon on a recently rebooted or updated VMware ESXi host.

  • Navigating to Host > Configure > System > Time Configuration and clicking TEST SERVICES returns a failure.
  • The vSphere Client displays the error: "Configuration is not working normally."
  • Running ntpq -p via the ESXi command line shows a reach value of 0 or a low value (e.g., 1, 3, 7, 15) rather than 377.

Environment

  • VMware ESXi 7.x
  • VMware ESXi 8.x
  • VMware vCenter Server 7.x
  • VMware vCenter Server 8.x

Cause

The failure is caused by a transient clock slew state. Immediately after a host reboot or NTP service restart, the ntpd daemon requires a minimum of eight successful polling intervals (approximately 5 to 15 minutes) to reach a "synchronized" state (Reach 377). If the service test is executed before this cycle completes, vCenter interprets the lack of an active synchronization lock as a configuration failure.

Resolution

To resolve this issue and confirm stable synchronization, follow these steps:

  1. Verify Initial Connectivity
    Log in to the ESXi host via SSH and verify the management interface can reach the NTP server: vmkping -I vmk0 ###.###.###.###

  2. Monitor Synchronization Progress
    Monitor the polling status to confirm the reach value is increasing: watch ntpq -p

  3. Allow Synchronization Window
    Wait 10–15 minutes without modifying the configuration. The TEST SERVICES will continue to fail until the reach column shows 377.

  4. Re-test in vSphere Client
    Once ntpq -p confirms a reach of 377, return to the vSphere Client and select TEST SERVICES again. The status should now report as successful.

  5. Address Persistent Failure
    If the test fails after 15 minutes, ensure UDP port 123 is open bidirectionally.
    If using ESXi 8.0 Update 3, verify the build version. Fixed in release ESXi 8.0 Update 3b and higher. See Download Broadcom products and software for steps to download this release.

Additional Information

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