Raise the Forest Functional Level
Applies To: Windows Server 2008
When you install Active Directory Domain Services (AD DS), a set of basic Active Directory features is enabled by default. In addition to the basic Active Directory features on individual domain controllers, there are new domain-wide and forest-wide Active Directory features available when all domain controllers in a domain or forest are running a later version of Windows Server.
To enable new forest-wide features, all domain controllers in the forest must run the version of Windows Server that corresponds to the forest functional level value or a later version, and the forest functional level must be raised to that value. For example, to enable Active Directory Recycle Bin, all domain controllers must run Windows Server 2008 R2 or Windows Server 2012 and the forest functional level must be raised to at least Windows Server 2008 R2.
Membership in Enterprise Admins , or equivalent, is the minimum required to complete this procedure. Review details about using the appropriate accounts and group memberships at Local and Domain Default Groups (https://go.microsoft.com/fwlink/?LinkId=83477).
To raise the forest functional level
Open Active Directory Domains and Trusts. To open Active Directory Domains and Trusts, click Start , click Administrative Tools , and then click Active Directory Domains and Trusts .
In the console tree, right-click Active Directory Domains and Trusts , and then click Raise Forest Functional Level .
In Select an available forest functional level , select the value and then click Raise .
After you set the forest functional level to a certain value, you cannot roll back or lower the forest functional level, with the following exception: after you raise the forest functional level to Windows Server 2012, you can lower it to Windows Server 2008 R2. If Active Directory Recycle Bin has not been enabled, you can also lower the forest functional level from Windows Server 2012 back to Windows Server 2008 R2 or Windows Server 2008 or from Windows Server 2008 R2 back to Windows Server 2008. If the forest functional level is set to Windows Server 2008 R2, it cannot be rolled back, for example, to Windows Server 2003. For more information, see Understanding Active Directory Domain Services (AD DS) Functional Levels.
To perform this procedure, you must be a member of the Enterprise Admins group in AD DS, or you must have been delegated the appropriate authority. As a security best practice, consider using Run as to perform this procedure. For more information, search for "using run as" in Help and Support.
If you are not able to raise the forest functional level, you can click Save As in the Raise Forest Functional Level dialog box to save a log file that specifies which domain controllers in the forest still need to be upgraded to a later version.
The current forest functional level is displayed under Current forest functional level in the Raise Forest Functional Level dialog box.
You can also perform the task in this procedure by using the Active Directory module for Windows PowerShell. For more information, see Set-ADForestMode.