Link state information is used to determine whether or not email should be routed using a particular Exchange Server connector. If the link state information marks a connector as "down," that connector will not be used until the link state changes.
The link state for a given Exchange Server connector is polled every 10 minutes. A connector will not be utilized if its connection wavers anytime within that window -- even if it is actually operational at some point during the poll period.
If a link fluctuates a great deal within a 10-minute window, some administrators will turn off link state information for a connector to reduce the amount of traffic generated by the link state signals.
It's also a good idea to disable link state for a given connector if it interacts poorly with an SMTP smart host.
On his blog, James Chong has identified one such instance when an Exchange SMTP connector to smart hosts stops responding. In such a case, the Exchange Server SMTP connector can only be restarted by rebooting the system or deleting and recreating the SMTP connector.
Future issues were circumvented by suppressing link state data from the SMTP connector. However, this approach can only be used with an SMTP connector if link state information is disabled system-wide.
To disable the use of link state information by all connectors, you have to edit the registry on the Exchange server with the connectors in question:
- Go to the key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet \Services\RESvc\Parameters.
- Add a new REG_DWORD value in this key named SuppressStateChanges and set it to 1.
- Restart the system (or at least Exchange Server services).
Note that this doesn't stop Exchange servers from propagating existing link state data between one another. It only stops connectors from generating link state traffic.
As a side note, connectors have an option labeled "Any local server can send over this connector." If you use the default setting of this option for a routing group connector, the connector state will always be marked as "up," and link state traffic for that connector will not be generated. This option will not work for SMTP or X.400 connectors, but the above fix for SMTP smart hosts will solve this problem.
About the author: Serdar Yegulalp is editor of the Windows Power Users Newsletter.
Do you have comments on this tip? Let us know.
Related information from SearchExchange.com:
Expert Advice: What are the major security issues involved with SMTP relay?
Expert Advice: Should Exchange utilitize an SMTP connector for internal email?
Tip: Migrating Exchange 5.5 connectors and services to Exchange 2003
Reference Center: SMTP tips and resources
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