Raising the Functional Level

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

When you deploy the first Windows Server 2003–based domain controller in your forest root domain, the forest operates by default at the Windows 2000 forest functional level, and the domain operates by default at the Windows 2000 mixed functional level. If your organization has only Windows NT 4.0 domains and your forest design requires upgrading Windows NT 4.0 domains and joining them to this Active Directory forest, you might want to raise the forest functional level to Windows Server 2003 interim after you deploy the forest root domain and before you begin the process for upgrading your Windows NT 4.0 domain to Windows Server 2003 Active Directory. If you raise the forest functional level to Windows Server 2003 interim, you can take advantage of the advanced features available at that functional level.

Figure 6.8 shows raising the functional level as the last step in the forest root domain deployment process.

Figure 6.8   Raising the Functional Level

Although the Windows Server 2003 domain functional level provides a number of features and advantages, only enable this functional level when your environment is ready and all of your Windows NT 4.0–based backup domain controllers (BDCs) have been upgraded.

Although it is possible for a domain to include both Windows NT 4.0–based and Windows Server 2003–based domain controllers, the Windows Server 2003 domain functional level provides more features.

When you have determined that your environment is ready, use Active Directory Domains and Trusts to enable the Windows Server 2003 domain functional level.

After all domains are operating at the Windows Server 2003 functional level, raise the forest functional level to Windows Server 2003 to take advantage of all Windows Server 2003 forest-level features.

To determine when to raise the functional level, and for procedures to perform those tasks, see "Enabling Advanced Windows Server 2003 Active Directory Features" in this book. For more information about upgrading Windows NT domains to Windows Server 2003 Active Directory, see "Upgrading Windows NT 4.0 Domains to Windows Server 2003 Active Directory" in this book.