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DaisyZhou-MSFT avatar image
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DaisyZhou-MSFT asked heyneke answered

raise the functional level

Hi,
We are looking to raise our domain and forest functional level from Windows 2008 R2 to Windows 2016 once the upgrade of our domain controllers is completed.
What's the impact if we raise the functional level from Windows 2008 R2 to Windows 2016 ?

Source link:
https://social.technet.microsoft.com/Forums/windowsserver/en-US/3ca9b692-8640-4755-86b4-de234cf8b5ad/raise-the-functional-level?forum=winserverDS

windows-active-directory
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FanFan-MSFT avatar image
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FanFan-MSFT answered

Hi,


Thank you for posting here.


According to our description, we would like to know whether there is any impact if we raise the functional level from Windows 2008 R2 to Windows 2016.


Once the Functional Level has been upgraded, new DCs on running on downlevel versions of Windows Server cannot be added to the domain or forest. To prevent these issues from arising, a new DC must be at the same level, or greater, than the functional level of the domain or forest.


The second restriction, for which there is a limited exception on Windows Server 2008 R2, is that once upgraded, the Domain or Forest Functional Level cannot later be downgraded.


The process of raising DFL/FFL is not a reversible operation without restore. Before proceeding further with the change, please review our AD environment. Make sure that our AD environment is healthy.


We can set the domain functional level to a value that is equal to or higher than the forest functional level. Also, we will need to have DCs that are running OS with the same level as DFL or higher.


For more information, please refer to:


Understanding Active Directory Domain Services (AD DS) Functional Levels
https://docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-server-2008-R2-and-2008/cc754918(v=ws.10)?redirectedfrom=MSDN


What is the Impact of Upgrading the Domain or Forest Functional Level?
https://docs.microsoft.com/en-us/archive/blogs/askds/what-is-the-impact-of-upgrading-the-domain-or-forest-functional-level


Hope the information is helpful. Please let us know if we would like further assistance.

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MiguelFra avatar image
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MiguelFra answered

Hello Daisy,

Once you raise the functional level, servers with lower OS'es than the ones below cannot be used as DC's:

•Windows Server 2019
•Windows Server 2016

Here's is a more detailed list of changes that may affect you.

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

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heyneke avatar image
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heyneke answered heyneke edited

One of the most well know considerations is your Exchange deployment if you have this in your environment. There are specific functional levels supported depending on the update version of Exchange. That being said. Did you know that you can lower the forest functional level back to Server 2008 R2 if you run into problems. Always have your DR plan ready should anything go wrong with the Schema updates for example.

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