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Add Additional Windows 2003 Domain Controller on an existing Windows 2008 Domain

Hello Experts,

I have an existing domain controller that runs Windows Server 2008 R2 Enterprise.
I would like to add a Windows Server 2003 Enterprise as a replica/additional domain controller.

Q1) what procedure should I follow? (Please post in detail; I have never done this before)

As far as I know while creating Active Directory on Windows Server 2008 the administrator must select that the domain should be compatible with Windows Server 2003.
But my server came with pre-configured Active Directory and I don’t know if the above option is selected.

Q2) How should I find if Active Directory of current Windows Server 2008 installation is compatible with Windows 2003 Domains or not?
Watch Question

Check the Domain Functional Level
Top Expert 2012

If your current domain and forest levels are set to Windows 2008 Server then you will not be able to add a Windows 2003 Server as a DC.


Top Expert 2013

As long as your functional level is not at 2008 or 2008 R2 you can add a 2003 box.  You would just add it and then promote it using dcpromo.

Why not add another Windows 2008 R2 box?


Lee W, MVPTechnology and Business Process Advisor
Most Valuable Expert 2013

> But my server came with pre-configured Active Directory
What do you mean by this?  Someone installed Active Directory for you?  Your server CANNOT legally come pre-configured with Active Directory.  You have to accept a EULA when you turn it on.  When you install AD, you do not select the domain functional level.  It is by default set to the lowest compatible with the version of AD (if I remember correctly).  In the case of 2008 and 2008 R2, I believe that's 2003.  So long as (as others have stated) your domain is at the correct functional level, you just run DCPROMO on the 2003 server and promote it, reading carefully the screens of the wizards.  I have found on occasion it may error at some point regarding the starting of a service - in my experience, I hit back a couple of times and restart the replication and it completes successfully.


Dear Experts,

The Windows Server Installation and Active Directory were created by an external partner.

Nowadays I don’t associate with this partner and I don’t know the configuration Functional Level selected on my Windows 2008 Domain.

For my case I think it should be configured as per below image:
Functional Level Options
Does anybody know if I could find what Functional level is already selected for my case?

Yes Windows Server 2003 functional level will allow you to deploy a Windows Server 2003 Domain Controller
Technology and Business Process Advisor
Most Valuable Expert 2013
Don't recall the last time I installed JUST a 2008 domain from scratch... so I got that part wrong, apparently it does prompt you for the forest functional level nowadays...

In any case, just review this document on checking and setting the levels - (the forest level is at the bottom, I believe):

And of course, you can "check" by not actually doing anything to change it.



Following leew instructions I have found that my current domain functional level is Windows Server 2003.
So Q2 was answered (Thank you Leew).

For Q1 what I should do in order to add my Windows 2003 Server as additional DC?
Do I need to run Aprep on Windows Server 2008 or something else?
Lee W, MVPTechnology and Business Process Advisor
Most Valuable Expert 2013
All you need to do is run DCPROMO.  All the needed information is in AD already to allow a 2003 DC.