Hello there,
The limitations regarding the forest and domain functional levels in Windows Active Directory can vary depending on the specific functional level and the features available in the Active Directory version. Here are some general considerations and limitations:
Compatibility: When raising the functional level to a newer version, ensure that all domain controllers in the domain or forest are running an operating system version that supports that functional level. Upgrading the functional level without updating all domain controllers can cause compatibility issues.
Down-Level Domain Controllers: Once the functional level is raised to a higher version, it may prevent the addition of down-level domain controllers running older versions of Windows Server. This is because the newer functional levels introduce features and capabilities that are not supported by older operating systems.
Feature Availability: Certain features and functionalities introduced in newer functional levels may not be available or fully supported when operating at lower functional levels. Raising the functional level allows the use of these advanced features and enhancements.
Domain and Forest Trusts: The functional level of the domain or forest may impact the ability to establish trusts with other domains or forests. Some trust types may require a specific functional level to be in place.
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