AD Forest and Domain functional levels

Question

Dear team,

We have the following scenario: one AD forest with one domain, having Forest functional level Win Server 2008, and all Domain Controllers running on Win Server 2012 R2.

There is a need to upgrade the Win Server version of the domain controllers, and consequently the domain and forest functional levels. However, some servers are still running the Win Server 2003 and 2008 legacy versions that still rely on SMBv1, and we need to make sure that they will not be affected. We are thinking of creating a child domain within the same forest, and join the legacy servers to it, and keep the parent domain for the rest of the servers. Would it be possible to keep the domain functional level for the child domain at 2008, and at the same time upgrade the domain functional level of the parent domain to 2022?

Regards,

Answer 1

Hello Micheal Mallo,

Thank you for posting in Q&A forum.

There is no 2022 functional level, there is 2025 or 2016 or lower functional level.

https://learn.microsoft.com/en-us/windows-server/identity/ad-ds/active-directory-functional-levels

When you deploy AD DS, set the domain and forest functional levels to the highest value that your environment can support in order to use as many AD DS features as possible. When you deploy a new forest, you need to set both the forest and domain functional levels. You can set the domain functional level to a value that's higher than the forest functional level, but you can't set the domain functional level to a value lower than the forest functional level.

If you keep forest functional level 2008, you can set child domain functional level as 2008 or higher.

I hope the information above is helpful.

If you have any questions or concerns, please feel free to let us know.

Best Regards,

Daisy Zhou

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