Raising Windows 2003 Functional Levels

When a migration or clean installation is completed, Windows Server 2003 does not immediately begin functioning at a native mode level. This is the case even when all domain controllers have been migrated to Windows 2003.

The Functionality of Mixed Mode Environments

When considering raising functional level in Windows 2003, you should understand the functionality of Mixed mode environments cannot be returned after the mode has been changed to native.

This section will focus on domain functionality with Windows 2003 and how and when it is best to raise functional levels to raise domain functional levels.

Domain Functional Levels

Windows 2003 supports four functional levels. These levels allow Active Directory to include down level domain controllers during an upgrade process. Review the following information to understand the different functional levels before determining which is best for your organization:

• Windows 2000 Mixed Mode Domain When Windows Server 2003 is installed into a Windows 2000 Active Directory forest that is running in Mixed mode, it essentially means that Windows 2003 domain controllers will be able to communicate with Windows NT and Windows 2000 domain controllers throughout the forest. This is the most limiting of the functional levels, however, because functionality such as Universal Groups, group nesting, and enhanced security is absent from the domain. This is typically a temporary level to run in, as it is seen more as a path towards eventual upgrade.

• Windows 2000 Native Mode Installed into a Windows 2000 Active Directory that is running in Windows 2000 Native mode, Windows 2003 servers will run at a Windows 2000 functional level. Only Windows 2000 and Windows 2003 server domain controllers will be able to exist in this environment.

• Interim Level Interim mode gives the Windows 2003 Active Directory the capability to interoperate with domains composed of Windows NT 4.0 domain controllers only. Although this is a confusing concept at first mention, the Windows 2003 Server Interim level does serve a purpose. In environments that seek to upgrade directly from NT 4.0 to Windows 2003 Active Directory, Interim mode allows 2003 servers to manage large groups more efficiently than if an existing Windows 2000 Active Directory exists. After all Windows NT domain controllers have been removed or upgraded, the functional levels can be raised.

• Windows Server 2003 Functional Level The most functional of all of the various levels, Windows Server 2003 Functional Level allows for full functionality of the Windows 2003 Domains server family products.

Raising Functional Levels

After each domain functional level has been raised, as well as the forest functional level, the Active Directory environment will be completely upgraded, and fully compliant with all of the Active Directory enhancements in Windows 2003. Functionality on this level opens up the environment to features such as schema deactivation , domain rename, domain controller rename, and cross-forest trusts.

After all domain controllers have been upgraded or replaced with Windows Server 2003, the domain and then the forest functional levels can be raised. To raise the domain functional level with Windows Server 2003, complete the following steps.

1. Ensure that all domain controllers in the forest are upgraded to Windows Server 2003.

2. Open Active Directory Domains and Trusts from the Administrative Tools.

3. In the left pane, right-click on Active Directory Domains and Trusts and the click Raise Domain Functional Level.

4. In the box labeled Select an Available Domain Functional Level, select Windows Server 2003, and then select Raise.

5. Click on OK, and then click OK again to complete the task.

6. Repeat the steps for all domains in the forest.

7. Perform the same steps on the forest root, except this time click Raise Forest Functional Level.