Domain functionality activates features that affect the whole domain and that domain only. The four domain functional levels, their corresponding features, and supported domain controllers are as follows:
Windows 2000 mixed (Default)
- Supported domain controllers: Microsoft Windows NT 4.0, Windows 2000, Windows Server 2003
- Activated features: local and global groups, global catalog support
Windows 2000 native
- Supported domain controllers: Windows 2000, Windows Server 2003
- Activated features: group nesting, universal groups, SID History, converting groups between security groups and distribution groups, you can raise domain levels by increasing the forest level settings
Windows Server 2003 interim
- Supported domain controllers: Windows NT 4.0, Windows Server 2003
- Supported features: There are no domain-wide features activated at this level. All domains in a forest are automatically raised to this level when the forest level increases to interim. This mode is only used when you upgrade domain controllers in Windows NT 4.0 domains to Windows Server 2003 domain controllers.
Windows Server 2003
- Supported domain controllers: Windows Server 2003
- Supported features: domain controller rename, logon timestamp attribute updated and replicated. User password support on the InetOrgPerson objectClass. Constrained delegation, you can redirect the Users and Computers containers.
Domains that are upgraded from Windows NT 4.0 or created by the promotion of a Windows Server 2003-based computer operate at the Windows 2000 mixed functional level. You can raise the domain functional level to either Windows 2000 native or Windows Server 2003.
After the domain functional level is raised, domain controllers that are running earlier operating systems cannot be introduced into the domain. For example, if you raise the domain functional level to Windows Server 2003, domain controllers that are running Windows 2000 Server cannot be added to that domain.
To check which functional level for our domain:
- Open the Active Directory Domains And Trusts console
- Right-click the particular domain whose functional level you want verify, and select Raise Domain Functional Level from the shortcut menu.
- The Raise Domain Functional Level dialog box opens.
- You can view the existing domain functional level for the domain in Current domain functional level.