Smoothing the road to a new messaging infrastructure
The move from Microsoft Exchange Server 5.5 to Exchange 2000 Server and the corresponding move from Windows NT to Windows 2000 are some of the most significant changes you'll make to your infrastructure in the near future. Because an Exchange 2000 migration requires some fundamental changes to your environment, setting out on the road to Exchange 2000 without understanding every detail of the migration isn't smart. In my experiences as a consultant with Compaq—migrating many tens of thousands of users—I've learned several tips that can help smooth that road from beginning to end. However, the tips assume you understand the basic concepts behind Exchange 2000 migrations; if you don't, you might want to save this article until after you've acquired foundational migration knowledge (for helpful Exchange 2000 migration references, see "Related Reading," page 96).
TIP 1: Recruit Sponsorship
Attracting the right level of organizational sponsorship might be an obvious first step on the road to migration, but broad-based management and technical support are crucial to a successful migration. Migration to Exchange 2000 cuts across many aspects of your environment. For example, you might need to significantly alter your Windows infrastructure, especially if you're migrating to Win2K at the same time you're migrating to Exchange 2000, and you'll need to modify your DNS infrastructure to support Active Directory (AD). You'll also probably need to revisit the hardware configurations for your Exchange servers.
Such infrastructure modifications typically involve multiple business units and locations and require financial backing from various parts of the organization. Consequently, you might meet resistance. To help ensure success, publicize the benefits of the migration within the organization, organize the migration effort as a series of separate subprojects centered on the individual technologies that you need to revamp, and make sure all key managerial and technical players buy into the effort.
TIP 2: Prepare your domain environment
Typically, the Exchange 5.5 and NT partnership gives rise to unwieldy domain infrastructures. Such domain models aren't ideal for Win2K, which is better suited to leaner domain models. Before you migrate, you should streamline your domain structure. (For information about consolidating domains, see Robert McIntosh, "Windows 2000 Domain Consolidation," http://www.win2000mag.com, InstantDoc ID 8933.)
Exchange 2000 requires you to run Domainprep in every domain that will host Exchange 2000 user or server accounts. Thus, the fewer domains you have, the less work you need to do to prepare those domains. Furthermore, a simple domain model can help reduce the number of connection agreements (CAs) you need. Typically, you need a CA from each Exchange 5.5 site. So long as the recipients from each Exchange 5.5 site are homed within one domain, the number of CAs you need is minimized. Increasing the number of domains means that recipients from one Exchange 5.5 site might need to replicate to another domain, increasing the number of CAs you need for that Exchange site.
Compaq's NT domain model consisted of more than 1800 domains. In the move to Win2K, Compaq flattened that structure to the four-domain model that Figure 1 shows. In the new model, each parent domain acts merely as a name placeholder; the child domains hold all user and machine accounts. In an ideal world, you'd be able to flatten all your domains into one domain. However, for various political and security reasons, that structure often isn't possible.
When preparing your domains, also ensure that the Win2K domains that will host your user accounts and groups are in native mode. This mode supports the use of Universal Security Groups (USGs), which Win2K typically requires to enforce access controls on Exchange 2000 public folders.
TIP 3: Ensure that AD is replicating
AD is crucial to the correct operation of Exchange 2000. Before you install Exchange 2000, you run Forestprep to add Exchange 2000 schema extensions and define the Exchange organization hierarchy in AD. Exchange 2000 stores all its configuration information, including that about servers, connectors, and routing groups, in AD's Configuration naming context (NC). By default, the Configuration NC replicates to all domain controllers (DCs) within the forest. When you run Forestprep on the first Exchange server you install, the server expects to find a definition of the Exchange organization in the Configuration NC. But if replication of the Configuration NC hasn't occurred (e.g., because of latency), the Exchange 2000 installation fails with errors. I've seen these failures occur time and again in Exchange 2000 deployments. In addition to migrating organization definitions, AD replication functionality is important for synchronizing information about users and contacts to all Global Catalog (GC) servers throughout the forest.
To assure successful installation, you need to devote sufficient attention to AD replication. You can use the ADSI Edit utility from the Win2K Server installation CD-ROM's Support Tools directory to check that data has been replicated. (For information about how to use this utility, see Sean Daily, Daily Answers, "The ADSI Edit Utility," March 2001.) Alternatively, you can use the Microsoft Windows 2000 Server Resource Kit's Replmon tool to monitor replication status. Replmon has the advantage of letting you force replication.