Domain Controller Functional Level
After the domain functional level is raised to a higher level it can only be changed back to an older level by using a forest recovery.
Domain controller functional level. The minimum requirement to add a windows server 2019 domain controller is a windows server 2008 functional level. There are no new forest or domain functional levels added in this release. Changing the domain functional level.
The domain also has to use dfs r as the engine to replicate sysvol. The functional level of the active directory domain and forest determines the available features that can be used in the domain and the windows server version you can use on domain controllers. The domain functional level can be changed by right clicking the domain and selecting raise domain functional level before doing this step you must ensure that all domain controllers are running the version s of windows that allow for the change.
Domain functional level dfl determines the features of a domain controller dc based on the windows server operating system os it runs on. What is the domain functional level dfl. For example a windows server 2008 functional level requires that all domain controllers have windows server 2008 or a later operating system installed in the domain or in the forest.