NTP configuration ignores 127.127.1.0 (Undisciplined Local Clock) from ESXi 6.5 and later and if no other NTP server provided in the configuration, ntpd fails to start

Products

• VMware vSphere ESXi

Issue/Introduction

Symptoms:

• NTP configuration ignores 127.127.1.0 (Undisciplined Local Clock) from ESXi 6.5 and later and if no other NTP server provided in the configuration, ntpd fails to start 

Cause

NTP daemon on ESXi host runs as a client. The daemon queries upstream servers and sets the system clock.
Specifying 127.127.1.0 configures ntpd to use the system's clock as a time source. This time source is categorized as "Undisciplined Local Clock" and not a best practice to use with ntpd.

Resolution

This is an expected behavior. If Synchronize guest time with host is enabled and NTP is not configured in ESXi, Virtual Machines are enabled to sync time with local clock through VMkernel .