Vmware ESXi 5.1 NTP and Windows Domain Time synchronization

Posted on 2013-11-22
Medium Priority
Last Modified: 2013-11-27
We have a Windows Domain , all servers are virtualized running on VMware ESXi 5.1 .

Each Virtual Guest is configured to receive time from the host configured through edit settings VMware Tools "Syncronize guest time with host"
I understand now that this could be bad for a domain controller, what is my best way to synchronize time ?

Also each of my ESXi host computers are configured to receive time from NTP servers ( and In Vsphere Client NTP client is running yet my 6 host machines do not have the same time some are off by more than a minute.  How do I properly configure NTP and make sure it is working ?

I have Windows guests Server 2003 / 2008 and 2012 .  Where should they be getting time ? from the DC's ? how do I force this to work ?

Thanks for your input.
Question by:Ekuskowski
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LVL 126

Assisted Solution

by:Andrew Hancock (VMware vExpert / EE MVE^2)
Andrew Hancock (VMware vExpert / EE MVE^2) earned 668 total points
ID: 39670294
How we setup our clients is as follows:-

1. ESXi/ESX Hosts are set to an external time source. (internet or your own time server)

2. DC, PDC emulator is set to the same external time source as in 1.

3. VMware Tools Sync time with host is disabled on ALL Windows VMs. They will get time from Domain.

4. Linux/Unix VMs are synced with external time source as in 1.

I also refer you to:-

VMware KB: Timekeeping best practices for Windows, including NTP

VMware KB: Troubleshooting NTP on ESX and ESXi 4.x / 5.x

Timekeeping In VirtualMachines Whitepaper
LVL 24

Assisted Solution

Sandeshdubey earned 1332 total points
ID: 39670853
You should configure authorative time server role on PDC and point the time sync to external windows time and disable the time sync from host server to VM.

Virtualizing Domain Controllers and the Windows Time Service(Virtualized DC Best Practices:

Configure authorative time server on the PDC role holder server below is the KB article for the same.http://support.microsoft.com/kb/816042

Please also make sure that udp port 123 which as direction the chosen NTP server is not blocked.

For other domain computers / servers, make sure that they are using NT5DS for time sync. More here: http://support.microsoft.com/kb/223184

Author Comment

ID: 39675922
I'm still not sure Why my VMware hosts are not keeping the correct time, I'm just going to call VMware to resolve that part of my issue

I have four domain controllers in my organization that each now gets its time from an external source (time.windows.com 0x9) .  Which I believe is just a Microsoft Default time source.

I have two Domain controllers at my main site and then at two remote sites I have one domain controller in each.

Should any of my domain controllers be getting time from another domain controller or is it ok to have them all access the same external time source ?
should I change the time source from the default (time.windows.com ? If I should change is there a particular NTP server I should be pointing at ?
LVL 24

Accepted Solution

Sandeshdubey earned 1332 total points
ID: 39676554
Refer below link to disable host to VM server.
You just need to configure NTP on PDC role holder server and other DC should be set to NT5DS.

Just execute below commands on DC.

PDC server.

net stop w32time
w32tm /unregister
w32tm /register
net start w32time
net time /setsntp:
net stop w32time & net start w32time
w32tm /config /manualpeerlist:pool.ntp.org /syncfromflags:manual /reliable:yes /update
w32tm /resync /rediscover
net stop w32time & net start w32time

NON PDC server

net stop w32time
w32tm /unregister
w32tm /register
net start w32time
net time /setsntp:
Net stop w32time & net start w32time
w32tm /config /syncfromflags:domhier /update
W32tm /resync /rediscover
net stop w32time & net start w32time

Author Closing Comment

ID: 39681852
As of now all my servers time is in sync, I mainly followed Sandeshdubey especially the straight forward commands that were posted. I still need to take care of my VMware host servers but for now I am ok.

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