Active Directory Time Issues, Help Explain?

We experienced an issue this morning having to do with Active Directory and System Times.  The system clocks on several of our servers and many of our clients became off by a couple of hours, which started causing issues on their next reboots.  Everything is working now, and I think I have a handle on WHAT happened, but I am trying to understand WHY it happened and how to rpevent it in the future.  Please comment and let me know what you know and any advice you can share.

We have five domain controllers spread between four sites (A, B, C, D).  I will call the DCs A1, A2, B1, C1, D1 just to make it easy.  
The "1's" are all Global Catalogs, serve as DHCP and DNS servers for their sites.  
All of the Active Directory Roles are held by server A1 except for the PDC Emulator, which is held by server A2.

Server A2 went offline yesterday for no more than 15 minutes due to a power failure.  It dropped, and came back fine.  This happened yesterday late afternoon around 5pm.  After this happened, the clocks of a lot of the workstations shifted by an hour.  It was determined that server B2, which is at a different site in another time zone started handling time operations for the domain.  When this happened the servers, the clients, and exchange all went out of synch and no one could connect to Exchange.

So I guess I am trying to figure out why a DC in another site assumed time operations for the domain and not the other server in the same site as the failed server.  Also, how do I control who takes on the failover responsibility?  Can I point every DC to an outside time source, or should I only point the PDC Emulator to the outside?

Please elt me know your thoughts.

abillzAsked:
Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

MikealclCommented:
Normally you only point the PDC emulator to a NTP server and then AD takes care of the rest.

I was under the impression that AD passed the time in UTC/GMT format, then the client adjust based on its time settings locally.

http://technet.microsoft.com/en-us/library/bb727060.aspx





0
maze-ukCommented:
Windows Time Service Tools and Settings: http://technet.microsoft.com/en-us/library/cc773263(WS.10).aspx

the PDC in your root domain must be configured to use either its own clock, either an external source.
Configure the Windows Time service on the PDC emulator: http://technet.microsoft.com/en-us/library/cc786897(WS.10).aspx

The rest of your machines (clients and DC) must be configured to use the domain hierarchy: (that is clients to PDC, PDC to root PDC)
Configure a client computer for automatic domain time synchronization: http://technet.microsoft.com/en-us/library/cc758905(WS.10).aspx

Check that no firewall prevents the connection to port UDP 123 on DCs. Check also the port if you use an external source for your PDC.
0

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Active Directory

From novice to tech pro — start learning today.

Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.