Active Directory, 3rd Edition

Functional Levels Explained

Now that you are sufficiently excited about the new features with Active Directory and improvements since Windows 2000, we will cover how you can actually enable these features in Windows Server 2003 . If you've already deployed Windows 2000 Active Directory, you are most certainly familiar with the domain mode concept. With Windows 2000 Active Directory, you had mixed- and native-mode domains. Domain mode simply dictated what operating systems were allowed to run on the domain controllers and nothing more. New features were enabled with the move to native mode, including universal security groups and enhanced group nesting to name a couple. Think of functional levels like domain modes, but taken a step further.

Windows Server 2003 functional levels are very similar to Windows 2000 domain modes from the standpoint that they dictate what operating systems can run on domain controllers, and they can only be increased or raised and never reversed. One common misunderstanding with domain modes, which hopefully will not be carried over to functional levels, is that they have virtually no impact on clients and what operating systems your clients run. For example, you can have Windows 9x clients in mixed- or native-mode Windows 2000 domains and also in domains that are at the Windows 2000 or Windows Server 2003 domain functional level.

Tip

For information about which operating systems are allowed at the various functional levels, check out Chapter 2.

An important ...