Forest & Domain Functional Levels

Question

Hi All,

We are about to raise the Domain & Forest Functional Levels on our Test and Live environments.

We have one forest and a sub Domain, both are Windows Server 2008 functional Levels. We have many trusts connected to these Domains.

I believe that we have to Raise all the Domain levels before we can raise the Forest Functional Level and wondered if that was right? Also, what about the trusts that are connected to our Domains and forest, how would it affect them?

I have only ever had to do this on one occasion. I wondered if there was anyone who could give me advice as to what I need to look out for and the possible pitfalls.

Regards.

Answer 1

Hello czql5v007,

Thank you for posting in Microsoft Community forum.

I believe that we have to Raise all the Domain levels before we can raise the Forest Functional Level and wondered if that was right?
A: Yes, you are right. Also, make sure all the DCs version are higher than 2008 before you raise Domain level.

How to raise Active Directory domain and forest functional levels - Windows Server | Microsoft Learn

Also, what about the trusts that are connected to our Domains and forest, how would it affect them?
A: It should be no affection. For more information, please read link below.

What is the Impact of Upgrading the Domain or Forest Functional Level? - Microsoft Community Hub

Here is other information for your references.

Before you upgrade the domain/forest functional level, understand the following:

1. Check that all domain controllers are working properly; 

    2. It is normal to check the AD replication between domain controllers. 

3. Back up all domain controllers using Windows built-in Windows back up tool; 

4. Ensure that all domain functional levels are equal to or higher than forest functional levels; 

5. Ensure that all domain controller operating systems are at or above the domain functional level; 

6. The domain function level can only be upgraded on the PDC simulation simulator operating host; 

7. Forest functional levels can only be upgraded on schema operations hosts. 

When upgrading the domain/forest functional level, pay attention to the following three points:

1. When the domain functional level/forest functional level is elevated, the Active Directory schema will be modified as the Active Directory schema exists throughout the forest.
2. Changing the domain or forest functional level does not affect applications that depend on Active Directory.

I hope the information above is helpful.

If you have any question or concern, please feel free to let us know.

Best Regards,
Daisy Zhou

Answer 2

Hi,

Thanks very much for the reply. It was pretty much what I expected.

I think I am right in stating that member servers have no relevance and only servers that are Domain Controllers in the Forest/Domain. The reason I ask is that there are some W2008 member servers on the Domain and will be after the upgrade to W2012.

Regards.

Answer 3

Hello czql5v007,

Thank you for your reply.

If you have any question or concern, please feel free to let us know.

Have a nice day!

Best Regards,
Daisy Zhou