Yes exactly, another post about NTP service and important role of time synchronization between virtual infrastructure components. In another post i described about a problem with ESXi v6.7 time setting and also talk about some of useful CLIs for the time configuration, manually ways or automated. But in a lab scenario with many versions of ESXi hypervisors (because of servers type we cannot upgrade some of them to higher version of ESXi) we planned to configure a NTP server as the "Time Source" of whole virtual environment (PSC/VC/ESXi hosts & so on).
But our first deployed NTP server was a Microsoft Windows Server 2012 and there was a deceptive issue. Although time configuration has been done correctly and time synchronization has occurred successfully, but when i was monitoring the NTP packets with tcpdump, suddenly i saw time shifting has been happened to another timestamp.
At the first step of T-shoot, i think it's maybe happened because of time zone of vCenter server (but it worked correctly) or not being same version of NTP client and NTP Server. (to check NTP version on ESXi, use NTP query utility: n
tpq --version) and also change ntp.conf file to set exact version of NTP. (vi /etc/ntp.conf and add "version #" to end of server line) But NTP is a backward compatible s
ervice as and i thought it's not reason of this matter.
So after more and more investigation about cause of the problem, we decided to change our NTP server, for example a Mikrotik router Appliance. and after initial setup and NTP config on the
Mikrotik OVF, we changed our time source. So after setting again the time manually with "esxcli hardware clock" and "esxcli system time" configure host time synchronization with NTP. Initial manual settings must be done because your time delta with NTP server must be less than 1min.
Then after restart NTP service on the host ( /etc/init.d/ntpd restart) i checked it again to make sure the problem has been resolved.
link of post in my personal blog: Undercity of Virtualization: Time differentiate between ESXi host & NTP Server