VMware – Setting up ESX NTP Time Sync

KB ID 0000798


Having your ESX Server running the correct time is quite important, and before you visit this subject, I would suggest you MAKE SURE the time is set in the ESX Servers BIOS, ie the internal clock is set correctly first. I’ve lost count of the amount of times I’ve seen Windows domains fall over because the ESX host has reverted to its BIOS time and replicated that time to its guests, suddenly your domain clocks are two years apart and carnage ensues!


Note: For this to work the hosts need to be able to communicate with public time servers over NTP (UDP Port 123), ensure your firewall has this port open or time sync will fail.

1. Connect to the host (or vCenter and drill down to the host(s)). Select the host in question > Configuration > Time Configuration > Properties > Tick NTP Client Enabled > Options > Add > Add in your public time server IPs > Tick ‘Restart NTP Service to apply changes’ > OK > OK.

ESX NTP Time Settings

Note: I’m in the UK so I’m using two time servers in this country, you may want to use one closer to home. = turnip.mc.man.ac.uk (Manchester University) = dir.mcc.ac.uk (Manchester University)

2. When you see the following all is well.

ESX NTP Time Sync

Note: If all these details are IN RED, then it has failed to sync, either be patient, try putting the host into and out of maintenance mode, or reboot it, if it continues to fail check it can see the public time servers on UDP port 123.

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Author: Migrated

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