When you install Active Directory Domain Services (AD DS) on a server running Windows Server 2008 R2, 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 Windows Server 2008 R2.
To enable new forest-wide features, all domain controllers in the forest must be running Windows Server 2008 R2, and the forest functional level must be raised to Windows Server 2008 R2.
Membership in Domain Admins or Enterprise Admins, or equivalent, is the minimum required to complete this procedure. Review details about using the appropriate accounts and group memberships at
 | 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, do one of the following:
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To raise the forest functional level to Windows Server 2008, click Windows Server 2008, and then click Raise.
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To raise the forest functional level to Windows Server 2008 R2, click Windows Server 2008 R2, and then click Raise.
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To raise the forest functional level to Windows Server 2008, click Windows Server 2008, and then click Raise.
 | Caution |
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Do not raise the forest functional level to Windows Server 2008 R2 if you have or will have any domain controllers running Windows Server 2008 or earlier. |
 | Important |
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After you set the forest functional level to a certain value, you cannot roll back or lower the forest functional level, with one exception: when you raise the forest functional level to Windows Server 2008 R2 and if Active Directory Recycle Bin is not enabled, you have the option of rolling the forest functional level back to Windows Server 2008. You can lower the forest functional level only from Windows Server 2008 R2 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. |
Additional considerations
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To perform this procedure, you must be a member of the Domain Admins group or 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.
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Windows Server 2003 is the minimum domain functional level required for raising the forest functional level to Windows Server 2008. Likewise, Windows Server 2008 is the minimum domain functional level required for raising the forest functional level to Windows Server 2008 R2.
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Before you raise the forest functional level to Windows Server 2008 R2, verify that all domains in the forest are set to the domain functional level of Windows Server 2008. Note that domains that are set to the domain functional level of Windows Server 2008 will automatically be raised to Windows Server 2008 R2 at the same time that the forest functional level is raised to Windows Server 2008 R2.
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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.
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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. To open the Active Directory module, click Start, click Administrative Tools, and then click Active Directory Module for Windows PowerShell. For more information, see Raise the Forest Functional Level (
https://go.microsoft.com/fwlink/?LinkId=137826 ). For more information about Windows PowerShell, see Windows PowerShell (https://go.microsoft.com/fwlink/?LinkID=102372 ).