A domain mode for running Microsoft Windows 2000 domain controllers that is backward compatible with domain controllers running the earlier Windows NT operating system. Domain controllers running in mixed mode use the Windows NT LAN Manager (NTLM) authentication protocol, allowing Windows 2000 Active Directory to work with downlevel Windows NT domain controllers.
Mixed mode has the following characteristics:
If you have a pure Windows 2000–based network, you should configure your domain controllers to run in native mode. A domain running in native mode supports multimaster replication and nested groups.
Windows 2000 domain controllers install in mixed mode by default when you run the Active Directory Installation Wizard. You can use the administrative tool Active Directory Users and Computers to change your domain controllers from mixed mode to native mode. However, you cannot change domain controllers back to mixed mode. After you upgrade all your downlevel domain controllers to Windows 2000, change all domain controllers to native mode in order to take advantage of multimaster replication, nesting of groups, and universal groups in Windows 2000.