Microsoft KB Archive/829577

= Mixed mode vs. native mode in Exchange Server 2003 =

Article ID: 829577

Article Last Modified on 11/10/2005

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APPLIES TO


 * Microsoft Exchange Server 2003 Standard Edition
 * Microsoft Exchange Server 2003 Enterprise Edition

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For a Microsoft Exchange 2000 Server version of this article, see 270143.



IN THIS TASK

 * SUMMARY
 * Mixed mode
 * Native mode
 * Determining the mode of the Exchange organization
 * Changing from mixed mode to native mode
 * REFERENCES



SUMMARY
A Microsoft Exchange Server 2003 organization can run in one of two modes of operation: mixed mode or native mode. This article describes the differences between mixed mode and native mode.

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Mixed mode
An organization that is running in mixed mode can handle all versions of Exchange Server. By default, Exchange 2003 is installed in mixed mode.

When you introduce an Exchange 2003 computer into an existing Microsoft Exchange Server 5.5 Service Pack 3 (SP3)-or-later site by using the installation process, Site Replication Service (SRS) and Active Directory Connector (ADC) are installed. If you upgrade an existing Exchange 5.5 computer to Exchange 2003, you must install ADC before you upgrade. However, SRS is automatically installed. These components work together to provide remote procedure call (RPC) replication within a site and mail-based replication among sites. ADC Connection Agreements between the Active Directory directory service and the SRS database are automatically established to enable directory replication.

To other Microsoft Exchange Server 4. , Exchange Server 5.0, and Exchange Server 5.5 computers in the site, the Exchange 2003 computer appears as just another server. The servers send out directory replication notifications as usual, and the SRS database requests changes just as earlier versions of Exchange Server request changes.

Mixed mode is designed to maintain backward compatibility, but mixed mode limits the system to the constraints that are imposed by earlier software releases. In a mixed-mode site, the rules that apply to earlier versions of Exchange Server also apply to Exchange 2003.

The following limitations apply to Exchange 2003 when it is running in mixed mode:
 * Exchange 5.0 sites and Exchange 5.5 sites are mapped directly to administrative groups.
 * Administrative groups are mapped directly to Exchange 5.0 sites and to Exchange 5.5 sites.
 * Routing group membership consists only of servers that are installed in the administrative groups.

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Native mode
An organization that is running in native mode can contain only computers that are running Microsoft Exchange 2000 Server or Exchange 2003 or later. New Exchange 5.0 or Exchange 5.5 computers cannot be introduced into the organization.

You can change an Exchange 2003 organization to native mode after all the servers are upgraded to Exchange 2000 or to Exchange 2003 when earlier release restrictions no longer apply. You cannot switch to native mode until you either upgrade or decommission all earlier versions of Exchange Server.

Exchange 2003 native mode includes the following functionality:


 * Routing groups can include servers from multiple administrative groups.
 * Exchange 2003 servers can be moved between routing groups.
 * Simple Mail Transfer Protocol (SMTP) is the default routing protocol.
 * Lightweight Directory Access Protocol (LDAP) queries can be used to create dynamic query-based distribution groups.
 * Routing bridgehead server pairs use 8BITMIME data transfers to provide significant bandwidth improvement over routing group connectors.
 * The Information Store service in Exchange 2003 automatically ignores and removes &quot;zombie&quot; Access Control Entries (ACEs) from the Exchange 5.5 servers that were previously used in an organization.

Note You cannot move servers between administrative groups in either mixed mode or native mode.

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Determining the mode of the Exchange organization
By default, an Exchange 2003 organization runs in mixed mode. To determine the mode that the Exchange Server 2003 organization is currently running in, follow these steps:
 * 1) Click Start, point to Programs, point to Microsoft Exchange, and then click System Manager.
 * 2) Right-click the organization that you want to determine the mode for, and then click Properties.
 * 3) Click the General tab.

Under Operation Mode, the operating mode of the organization is displayed.

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Changing from mixed mode to native mode
Note Before you can change an organization from mixed mode to native mode, all the computers in the organization must be running Exchange 2003 or Exchange 2000. Before you can upgrade computers that are running any version of Exchange 4.0 or that are running Exchange 5.0 to Exchange 2003, you must upgrade those computers to Exchange Server 5.5 Service Pack 3 because Exchange Server 4.0 or later and Exchange 5.0 cannot be upgraded directly to Exchange 2003.

Important After you change to native mode, you cannot change back to mixed mode. This is a one-time conversion. Therefore, you must fully understand the results before you continue.

After you upgrade or remove all versions of Exchange Server that are earlier than Exchange 2000, you can switch your Exchange 2003 organization to native mode by using Exchange System Manager. To do this, follow these steps:
 * 1) Click Start, point to Programs, point to Microsoft Exchange, and then click System Manager.
 * 2) Right-click the organization, and then click Properties.
 * 3) In the   Properties dialog box, click Change Mode under Change Operations Mode.
 * 4) Click Yes if you are sure that you want to permanently switch the organization's mode to native mode.

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