Child Domain, Forest and Domain Functional Levels

Sajith Silva
Sajith Silva used Ask the Experts™
on
Hi,

We have 7 domain controllers with 2008 domain functional level and 2003 forest functional level. I like to change the forest functional level to 2008. Also I want to add a child domain with a 2012 R2 domain controller

q1. Do I have to raise the forest functional level in all domain controllers or if I change it in the primary one will it replicate to others?
q2. When I add the 2012 R2 domain controller how do I tell it you work with 2008 domain functional level?

I don't have test system so I'm bit nervous doing this on the production before I get the correct knowledge.

Thank you.
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Systems Engineer
Commented:
q1:  you just have to raise the functional level on a single DC, that change will propagate throughout the domain.  

reference links:
- http://blogs.technet.com/b/askpfeplat/archive/2012/09/03/introducing-the-first-windows-server-2012-domain-controller.aspx
- http://kpytko.pl/2012/09/07/adding-first-windows-server-2012-domain-controller-within-windows-200320082008r2-network/
- http://support.microsoft.com/kb/322692
- http://msdn.microsoft.com/en-us/library/cc753104.aspx

q2:  when dcpromo'ing the 2012R2 server, it will assume the functional level that is currently in operation.

I recommend that you make a full backup (BMR with system state) of the server(s) that hold the FSMOs before you raise the functional level.  This way, if there are complications, you could just do a Bare Metal Restore on the original hardware.

Raising the functional levels is somewhat uneventful process.  Preparation is more involved than the actual execution of the task.  Which amounts to selecting the new level and pressing a button.

Dan

Author

Commented:
Thanks mate. this is very useful.

the new DC with 2012 is going to be a child domain. I will follow the same steps as creating a new 2012 domain right?
Dan McFaddenSystems Engineer
Commented:
The functional level relationship between the forest and child domains is that the child domains cannot be lower than the forest domain\s functional level.  But child domain could be at a higher functional level.

Reference link:  https://social.technet.microsoft.com/Forums/windowsserver/en-US/7d0ab7d2-ec29-4e87-8a41-474c0dcba16e/raising-domain-functional-level-on-child-domain?forum=winserverDS

So the process of creating a child domain is the same.  It will initially assume the functional level of the forest during creation.  If you want to raise the child domain's functional level, then do so after verifying that the new domain functions as expected.

Dan

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