Time sync loops

[blin]

We have a very interesting case. Hopefully I can explain it clearly.


We configured our DC1 as time source and it has been working over one year. Recently, our DC2 had a problem. Then we re-built C2 as VM running on Hyper-V. Since then we have a time issue and some computers have slow time. I found it was DC2 and changed it to correct time. After one week, we have the same problem. Here is the result of w32tm /monitor.


C:\Windows\system32>w32tm /monitor

2008DC1.chicagotech.net *** PDC ***[10.0.0.17:123]:

ICMP: 0ms delay

NTP: +0.0000000s offset from 2008DC1.chicagotech.net

RefID: tick.usno.navy.mil [192.5.41.40]

Stratum: 2

2008DC2.chicagotech.net[[::1]:123]:

ICMP: 0ms delay

NTP: -291.4078841s offset from 2008DC1.chicagotech.net

RefID: 80.84.77.86.rev.sfr.net [86.77.84.80]

Stratum: 2


Looks good. Right? But if I run w32tm /query /source, I get:

VM IC Time Synchronization Provider


OK, that is the problem. Since 2008DC2 is on Hyper-v Dell-HPV03, it also takes time from the physical computer Dell-HPV0 and Dell-HPV03 also gets time from CD2 (I don't know why). Now, it loops between 2008DC2 and Dell-HPV03 time sync. When I changed the time on 2008Dc2 last week, it gets slow time from Dell-HPV03. That is why we have the slower time on some computers. My solution is changing both Dell-HPV03 and DC2 time. So far so good.

1.The DC1 (or PDC) type is “NTP and DC2 type is “NT5D5”. Is this settings correct? If yes, why doesn’t DC2 sync the time from DC1? And why Dell-HPV03 sync the time from DC2?
2. I read a post and someone mentioned if the DC is running as VM, we should “disable the time synchronization and leave it up to the DC’s own functionality to synchronize time with other DC’s” If he is right, how do we “disable the time synchronization and leave it up to the DC’s own functionality to synchronize time with other DC’s”?

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[blin]

Hello,

please see http://blogs.msdn.com/b/virtual_pc_guy/ ... per-v.aspx about time settigns for VMs on Hyper-V.


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Best regards

Meinolf Weber
MVP, MCP, MCTS
Microsoft MVP - Directory Services
My Blog: http://msmvps.com/blogs/mweber/

[blin]

Meinolf's link should explain everything. In summary, "partially" disable the HyperV host's time service.

.




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Ace Fekay
MVP, MCT, MCITP EA, MCTS Windows 2008/R2, Exchange 2007 & Exchange 2010, Exchange 2010 EA, MCSE & MCSA 2003/2000, MCSA Messaging 2003
Microsoft Certified Trainer
Microsoft MVP - Directory Services
Complete List of Technical Blogs: http://www.delawarecountycomputerconsul ... lblogs.php

[blin]

Quoted from the Microsoft article: :
To partially disable the Hyper-V time synchronization provider, leave Time synchronization enabled under Integration Services and run the following command from an elevated command prompt on the guest domain controller:

reg add HKLM\SYSTEM\CurrentControlSet\Services\W32Time\TimeProviders\VMICTimeProvider /v Enabled /t reg_dword /d 0
This command stops Windows Time service (W32Time) from using Hyper-V time synchronization integration when the guest domain controller’s operating system is started. With this setting disabled, the Hyper-V time synchronization provider is only used if the guest domain controller is rebooted or restored from a Saved state.

It is important to ensure that your host machine is syncing with a reliable time service to avoid any time skews".

Here is the result:

C:\Windows\system32>reg add HKLM\SYSTEM\CurrentControlSet\Services\W32Time\TimeP

roviders\VMICTimeProvider /v Enabled /t reg_dword /d 0

Value Enabled exists, overwrite(Yes/No)? y

The operation completed successfully.

C:\Windows\system32>w32tm /query /source

VM IC Time Synchronization Provider

It seems to me, it still sync with host. Any suggestions?

[blin]

Did you restart the time service?

net stop w32time
net start w32time

.

Personally, despite the recommendations, I usually just disable it and allow the machines to synch with the hierarchy.

.Ace Fekay
MVP, MCT, MCITP EA, MCTS Windows 2008/R2, Exchange 2007 & Exchange 2010, Exchange 2010 EA, MCSE & MCSA 2003/2000, MCSA Messaging 2003
Microsoft Certified Trainer
Microsoft MVP - Directory Services
Complete List of Technical Blogs: http://www.delawarecountycomputerconsul ... lblogs.php

[blin]

After restarting the Time service, it synchronizes with the DC1. Thank you.

1.“I usually just disable it and allow the machines to synch with the hierarchy”. Do you mean disable Time synchronization under Integration Services?
2.I have these settings: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Config\AnnounceFlags = 5 and Type = NTP on Our DC1
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Config\AnnounceFlags = 10 and Type = NT5DS on Our DC2.

Why some computers sync with DC2?

[blin]

time sync is done with one of the available DCs from domain members, ONLY DCs sync with the PDCEmulator. And this also will take some time until the time sync jumps in. Restarting the time service is recommended if you change the settings.

Best regards

Meinolf Weber
MVP, MCP, MCTS
Microsoft MVP - Directory Services
My Blog: http://msmvps.com/blogs/mweber/