Lesson 3: Mixed Mode and Native Mode

When planning your Exchange Server 2003 deployment, you'll need to consider in which mode your Exchange organization will operate. Since Exchange installs automatically in mixed mode, it's not critical that you make the decision initially; however, it is important particularly if you are currently supporting or migrating from an Exchange Server 5.5 environment.

After this lesson, you will be able to

• Understand the concepts behind mixed mode and native mode operation

• Identify the benefits and limitations of mixed mode

• Identify the benefits and limitations of native mode

• Understand when it is appropriate to convert from mixed mode to native mode

Estimated lesson time: 25 minutes

Mixed Mode and Native Mode Concepts

An Exchange Server 2003 organization can operate in one of two modes: native mode or mixed mode. Native mode offers full Exchange Server 2003 functionality, while mixed mode offers limited Exchange Server 2003 functionality but the benefit of interoperability between Exchange Server 2003 and Exchange Server 5.5. When you install Exchange Server 2003, your Exchange organization operates in mixed mode by default. This default setting ensures past and future interoperability with previous versions of Exchange. For example, you have the ability to install a server running Exchange Server 5.5 at a future date, even if no servers running Exchange Server 5.5 exist in the organization at the time of installation. You might encounter such a situation if your organization acquires another organization that is still running Exchange Server 5.5.

The concept of mixed mode and native mode organizations is similar to the concept of mixed mode and native mode domains in Active Directory. These are called modes in Windows 2000 Server and functional levels in Windows Server 2003, but the terms refer to the same thing. The similarity exists in terms of limiting new features that won't work on previous product versions versus exposing all of the new functionality. What mode you choose has tradeoffs between functionality and backwards compatibility. No direct relationship exists between the mode of the domain and the mode of an Exchange organization. With Exchange Server 2003, you can select native mode and mixed mode only at an organizational level.

Exam Tip

When an organization is in native mode, you only have servers running Exchange 2000 Server and Exchange Server 2003. Servers running Exchange 2000 Server and Exchange Server 2003 can coexist in native mode, so be aware of this when you come across scenarios where servers running Exchange 2000 Server are thrown into the mix.

A comparison of the benefits and limitations of each mode is useful in demonstrating the importance of the choice of mode for your Exchange Server 2003 organization. A particular benefit or limitation may be the deciding factor in your deployment plan, as to whether you need to convert to native mode as soon as possible in order to take advantage of native mode features, or whether you should stay in mixed mode to support previous versions of Exchange Server, previous applications, or connectors.

Mixed Mode Benefits and Limitations

The ability to operate an Exchange organization in mixed mode exists for backward compatibility with previous versions of Exchange Server and other software that relies on it. The differences between mixed mode and native mode are primarily concerned with the concept of administrative groups and routing groups. Mixed mode exists mainly to bridge the gap between Exchange Server 5.5 sites and Exchange 2000 Server and Exchange Server 2003 organizations by forcing Exchange 2000 Server and Exchange Server 2003 to operate within the boundaries of Exchange Server 5.5 sites. Administrative groups and routing groups cannot be managed independently in mixed mode. In other words, administrative groups and routing groups are mapped directly to sites and therefore do not have the flexibility that they have when the Exchange organization is operating in native mode.

Benefits of Mixed Mode

Running your Exchange organization in mixed mode ensures future interoperability between Exchange Server 2003 and previous versions of Exchange. The benefits of operating in mixed mode include the following:

• Interoperability between servers running Exchange Server 2003 and Exchange Server 5.5.

  • Routing between Exchange Server 2003 and Exchange Server 5.5 is seamless.

  • Exchange Server 2003 can use existing Exchange Server 5.5 connectors and gateways to connect to foreign e-mail systems and route e-mail messages.

  • Both Exchange Server 5.5 objects (users, custom recipients, and distribution lists) and Exchange Server 2003 objects (users, contacts, and groups) can be managed from Active Directory.

  • Public folders replicated between Exchange Server 2003 and Exchange Server 5.5 can be securely accessed from clients on either system.

• You have the option to install servers running Exchange Server 5.5 at a later date.

• All Exchange Server 5.5 directory service objects such as servers and connectors are replicated to Exchange Server 2003 and are displayed in the Exchange System Manager console.

Limitations of Mixed Mode

When your Exchange organization is operating in mixed mode, there are limitations and issues you must consider, such as the following:

• Exchange Server 5.5 sites are mapped directly to administrative groups.

• Administrative groups are mapped directly to Exchange Server 5.5 sites, which means that you cannot create administrative groups independent of the routing infrastructure.

• You can only move mailboxes between servers that are in the same administrative group.

• Routing group membership must consist only of servers installed in the administrative group that is defined with the routing group.

• You can move servers between routing groups, but all members of all routing groups must be members of the same administrative group.

• Exchange 5.5 system objects present read-only properties when viewed from Exchange System Manager.

• Some commands may not always function as you would expect them to due to interaction between older and newer components and management tools. For example, you cannot view the resource tables of an Exchange Server 5.5 server's database with Exchange System Manager.

Real World: Mixed Mode Administration

In an Exchange Server 5.5 site, not only are all servers managed as a single group, but all servers have reliable, high-speed connectivity for sending messages to one another. However, when an Exchange Server 2003 organization is in mixed mode and Exchange 5.x sites are mapped one-to-one with administrative groups, you can subdivide the routing structure for the servers running Exchange Server 2003 in the collection using routing groups. A server cannot belong to a routing group that is held under a different administrative group.

Because of the limitations of mixed mode, most organizations opt to convert to native mode unless they have a specific need to support Exchange Server 5.5 servers and sites.

Native Mode Advantages

Once an Exchange organization is converted from mixed mode to native mode, the organization is no longer interoperable with systems running Exchange Server 5.5. Exchange organizations operating in native mode can contain servers running both Exchange 2000 Server and Exchange Server 2003, and you can convert an Exchange organization to native mode only when all of the Exchange servers in it are running Exchange 2000 Server and Exchange Server 2003.

Convert your Exchange organization to native mode if the following apply:

• You do not have any servers running Exchange Server 5.5 in your organization (you've either migrated or decommissioned all of them or never had any to begin with).

• You have no plans to add servers running Exchange Server 5.5 to your organization in the future, such as a result of a merger or the acquisition of a company with servers running Exchange Server 5.5.

• Your organization will never require interoperability with servers running Exchange Server 5.5.

• Your organization does not use any connectors or gateway applications that run only on Exchange Server 5.5.

  Important

  Once you convert from mixed mode to native mode, the organization is no longer interoperable with Exchange Server 5.5 systems. That isn't to say that you won't be able to send or receive e-mail with Exchange Server 5.5 servers, but you won't be able to have seamless integration in the same Exchange organization. It is important to note that converting to native mode is a one-time, one-way operation that cannot be reversed at a later date.

Advantages of Native Mode

Running an Exchange organization in native mode gives you the full functionality and flexibility of Exchange Server 2003 when you manage your messaging system.

• Greater flexibility for defining routing groups and administrative groups. Since administrative groups are not tied to Exchange Server 5.5 sites, you can utilize the full functionality of the administrative group model. (This issue is discussed further in Chapter 3, Lesson 3.)

• The ability to move mailboxes between servers in different administrative groups. (This issue is discussed further in Chapter 7, Lesson 3.)

• The ability to configure administrative and routing groups independent of each other since they are no longer connected to fit the site model. (This issue is discussed further in Chapter 3, Lesson 3.)

• Query-based distribution groups (QDGs) can be created only in a native-mode Exchange organization. (This issue is discussed further in Chapter 7, Lesson 2.)

• If routing bridgehead pairs are upgraded to Exchange Server 2003 in a native-mode organization, they will use 8BITMIME data transfers instead of converting down to 7-bit. This equates to considerably less traffic over WAN connections when compared to Routing Group Connectors. (This issue is discussed further in Chapter 5, Lesson 1.)

Converting to Native Mode

Converting to native mode is accomplished through Exchange System Manager, by right-clicking on the organization name at the top of the window and clicking Properties. This brings up the property sheet shown in Figure 3-2.

Figure 3-2: The organization's property sheet

As shown in Figure 3-2, there is a Change Mode button on the General tab. The button will be unavailable if you are in native mode, but if you are in the default mixed mode, you can click the button to change the mode. When you do, you will receive a warning message that advises you that once the operation is complete, you will not be able to convert back to mixed mode.

Lesson Review

The following questions are intended to reinforce key information presented in this lesson. If you are unable to answer a question, review the lesson materials and then try the question again. You can find answers to the questions in the "Questions and Answers" section at the end of this chapter.

1. Which of the following statements are true about an Exchange organization operating in mixed mode?

   1. Administrative groups are mapped to Exchange Server 5.5 sites.

   2. You can move mailboxes between servers in different administrative groups.

   3. You can move mailboxes between servers in the same administrative group.

   4. You can edit Exchange Server 5.5 system data from Exchange System Manager.

   5. You can install servers running Exchange Server 5.5 in your organization, even if you have only servers running Exchange Server 2003 presently.

   6. Servers running Exchange Server 5.5 and Exchange Server 2003 can route mail seamlessly.

   7. You can configure administrative groups independently of routing groups.

2. You have a Windows Server 2003 domain that is operating at the mixed mode domain and forest functional level. You have installed Exchange Server 2003 into the domain, which has no other mail services running. You know that you will never need to support Exchange Server 5.5 installations, so you want to convert the Exchange organization to native mode. What do you need to do to accomplish this?

   1. Raise the domain functional level to native mode, and then change the Exchange Server 2003 mode to native mode.

   2. Raise the domain functional level to native mode, then raise the forest functional level to native mode, and then change the Exchange Server 2003 mode to native.

   3. Use Exchange System Manager to change the mode from mixed mode to native mode.

   4. Reinstall Exchange Server 2003 and choose native mode during the Setup program.

   5. Use the Active Directory Sites And Services console to change the mode for the Microsoft Exchange service from mixed mode to native mode.

3. You are the senior Exchange administrator for contoso.com, which has an Exchange organization consisting of servers running Exchange Server 5.5, Exchange 2000 Server, and Exchange Server 2003. Due to a recent company reorganization, there is a need to decentralize much of the Exchange administration duties to local branch offices. This will require you to convert the organization to native mode in order to gain the flexibility necessary with administrative groups. What servers must you upgrade prior to converting to native mode?

4. You have been asked to give a technology presentation for IT management in your company. The topic of the presentation is why the company should upgrade its existing Exchange Server 5.5 infrastructure to Exchange Server 2003. Management is partially sold on the idea after hearing about administrative groups; they want to migrate Exchange Server 5.5 to Exchange Server 2003 in eight of the company's 12 locations and to install Exchange Server 2003 to coexist with the existing Exchange Server 5.5 servers in two other locations. They like the idea of administrative groups not being tied to the physical layout of the network since some locations do not have their own administrators, and in some cases, administrators are responsible for more than one location. After you describe how this works in native mode in Exchange Server 2003, they ask if you can set it up so that the eight administrative groups with only servers running Exchange Server 2003 can be converted to native mode right away, leaving the other administrative groups to be converted later once Exchange Server 5.5 is able to be fully replaced. What do you tell them?

Lesson Summary

• Exchange Server 2003 installs in mixed mode by default. You must manually change the mode to native.

• Mixed mode is used to provide backwards compatibility with Exchange Server 5.5 servers and sites, with a loss of full Exchange Server 2003 administrative and routing group flexibility and functionality.

• Native mode allows administrative groups and routing groups to be configured independent of each other.

• Changing the mode from mixed mode to native mode is a one-time, one-way process. Once complete, it cannot be reversed.