Process (PID=). Topology Discovery failed, error 0x.

This event indicates that new topology could not be generated. If this is NOT the first topology discovery since system startup, the previously discovered topology will be used. However, topology discovery failure is usually a sign of a serious problem and needs to be investigated immediately. The following are the possible causes:

• All local domain controllers are down or deemed not suitable.
• Network problems are preventing the Exchange server from contacting the domain controllers.
• There are permissions problems.

• Look up the Lightweight Directory Access Protocol (LDAP) error description in the “Microsoft LDAP Error Codes” Knowledge Base article. To reach this article, search for “Microsoft LDAP Error Codes” on the Microsoft web site.
• Check local domain controllers to ensure that they are up and running and also check network connectivity to these domain controllers.
• Look for accompanying events in the application log. You may need to turn up logging for the Topology category of DSAccess to see these additional events.