Using Routing Groups in Native and Mixed Modes

In Exchange 2003 and Exchange 2000, the administrative and routing functions are split into different units:

• Administrative groups define the logical administrative boundary for Exchange servers.

• Routing groups define the physical routes that messages travel over the network.

If your Exchange organization is in native mode, where all servers are running Exchange 2000 or later, this split between administrative groups and routing groups helps you to create routing groups that span administrative groups, and move servers between routing groups that exist in different administrative groups. This functionality also helps you to separate routing and administrative functions. For example, you can administer servers in two central administrative groups, placing servers from each administrative group in different routing groups, based on your network topology.

However, the functionality of routing groups in mixed mode, where some servers are running Exchange 2003 or Exchange 2000 while others are running Exchange 5.5, is different from native mode. In mixed mode, you:

• Cannot have a routing group that spans multiple administrative groups.

• Cannot move servers between routing groups that exist in different administrative groups.

This is because the routing topology in Exchange 5.5 is defined by sites—logical combinations of servers connected by a high-bandwidth reliable network. Sites provide the functionality of both the administrative group and routing group in Exchange 2003 and Exchange 2000. This difference in routing topology limits routing groups in mixed mode.