A common problem that the Microsoft Exchange Best Practices Analyzer (ExBPA) finds during an Exchange Server 2007 environment-readiness analysis is the Link state suppression is not enabled error. It’s essential that you correct the error and suppress propagation of minor link-state updates between routing groups if you plan to create multiple Exchange 2007 routing group connectors to prevent routing loops. Unlike Exchange Server 2003 and Exchange 2000 Server, Exchange 2007 doesn’t use a link-state routing table and doesn’t support relay of link-state information. Instead, Exchange 2007 uses the Hub Transport server role on servers closest to the routing group connector failure point to ensure that messages can still be sent, rather than calculating alternate routes. If you have more than one routing group connector, you'll need to make the following registry change on all your Exchange 2003 and Exchange 2000 servers, to enable link-state suppression.
- Open the registry editor and navigate to HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\RESvc\Parameters.
- Right-click Parameters, select New, DWORD value. Name the new DWORD value SuppressStateChanges.
- Double-click SuppressStateChanges.
- In the Value data field, type 1, then press Enter.
- Close the registry editor and restart the SMTP service, the Microsoft Exchange Routing Engine service, and the Microsoft Exchange MTA Stacks service.
For more information about link-state-suppression, see technet.microsoft.com/en-us/library/aa996728(EXCHG.80).aspx, and for more information about message transport in Exchange 2007, see the Windows IT Pro article “Exchange 2007 Transforms Message Routing,” March 2007, InstantDoc ID 94859.