The functional level of the domain and forest corresponds to the “version” of your Active Directory environment and allows access to more or fewer features depending on the level of each.
Mainly this level change occurs when upgrading to Windows when replacing / migrating domain controllers. The version change may also be necessary for the installation of new service like Exchange, ADFS …
Before making this change, it must be verified that your environment will support the functional level increase.
Example: If you want to upgrade from 2003 to 2012, all domain controllers should at least work with Windows Server 2012.
Here are some notable features brought up during version upgrades:
- Replication of sysvol with DFS-R: Domain in 2008 level
- Active Directory Recycle Bin: Fence at 2008R2 level
The following manipulations are to be done on a domain controller.
Increase the functional level of the domain
Increase the functional level of the forest
It would have been possible to increase the functional level of the domain from this console, by right click on the domain
Increase the functional level of the domain and the forest with the ADAC console
Show functional level