When running the Exchange 2010 Pre-Deployment Analyzer you will probably get this message:
Before introducing Exchange Server 2010 into this topology, the 'SuppressStateChanges' configuration parameter should be set to '1' on server EXCHANGE03SERVER. This parameter is essential if you plan to create multiple connectors to the dedicated Exchange 2010 routing group.
Exchange Server 2003 includes functionality to detect automatically changes in the state of a link. This information can be used to inform other servers running Exchange Server 2003 that an alternative route should be used instead of the lowest cost primary route. Link state information is divided into major and minor changes. A major change occurs when the administrator changes the routing topology, such as the addition of a new connector or a cost change. Minor updates occur when the system automatically detects the failure or restoration of a link.
This feature works well in small to medium-sized organizations. However, in large multi-site environments, mass network fluctuation can cause link update floods for the minor version. To be truly effective, link state data must be broadcast to all the servers in the organization. Additionally, when state changes, the whole link state table is rebroadcast, which can cause a significant amount of data to be transmitted over the network. In these scenarios, it may be useful to suppress minor link state changes. The SuppressStateChanges registry value is a custom configuration setting used to suppress minor link state changes. When SuppressStateChanges is set to a value of 1 (or any value greater than 0), all link state traffic generated by a connector state change on this Exchange Server computer are suppressed.
In Exchange 2010 you want to link every Exchange 2003 routing group to the Exchange 2010 routing group to utilize the new hub transport technology for routing messages around your organisation. Because of this you must disable link stage suppression on all your Exchange 2003 servers before installing Exchange 2010.
To do this perform the following steps:
1.Open a registry editor, such as Regedit.exe or Regedt32.exe.
2.Navigate to HKLM\System\CurrentControlSet\Services\RESvc\Parameters.
3.Right-click Parameters and select New | DWORD value. Name the new DWORD value SuppressStateChanges.
5.Set Base to Decimal.
6.In the Value data field, enter 1.
7.Close the registry editor and then restart the Simple Mail Transfer Protocol (SMTP), the Microsoft Exchange Routing Engine, and the Microsoft Exchange MTA Stacks services for the change to take effect.