ESXi is unable to synchronize time after updating the A record of the NTP server

Products

• VMware vSphere ESXi
• VMware vSphere ESX 8.x
• VMware vSphere ESX 7.x

Issue/Introduction

 - The NTP server is registered on ESXi using its FQDN.
 - After updating the A record of the NTP server, ESXi becomes unable to synchronize with the NTP server

# localcli system ntp get
NtpSettings:
   Enabled: true
   Log level: warning
   PID: xxxxxx
   Runtime Seconds: xxxxxx
   Servers: ntp.example.org
   Service Providing Kernel Time: Network Time Protocol
   Time Service Enabled: true
   Time Synchronized: false

 - ESXi continues to reference the old IP address of the NTP server.

# ntpq -pn
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
*<OLD IP of NTP Server>   xxx.xxx.xxx.xxx       3 u  668 1024  377    8.896   +1.105   0.301

Cause

The ntpd service on ESXi persists in using the IP address resolved at startup for its communications with the NTP server.

Resolution

Restart the ntpd service using the following steps.

1. Connect to ESXi via SSH.
2. Execute the following command:

/etc/init.d/ntpd restart

Additional Information

Japanese KB: NTPサーバのAレコードを更新した後、ESXiが時刻同期できなくなる