time sources vcloud , vcenter , SSO, ESXi,AD ? what is best practice

what should I have pointed to what in the time domain , should I point my vCenter server to AD for its time or to the designated company wide UNIX time server ?
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Your AD  domain controller  should be configured and pointed to an external time source.

all Windows Servers will obtain time from Domain ensure any virtual machines hosted on ESXi do not sync with host.

ESXi servers point to same external time source as AD servers.
NAMEWITHELD12Author Commented:

is there any setting for vCenter ?
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
No, vCenter is a Windows Applicatio which takes it's time from the OS.
ESXi could also point to your AD server. Especially if you can't enlarge firewall rules to sync with and external time source.

If your vcenter is on a AD domain,

w32tm /config /syncfromflags:domhier /update

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... will re-enforce time sync (and update time) with any DC.

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Windows Server 2008

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