This Error 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. If it is the first topology discovery, most of the Exchange services will not start.
Topology discovery failure is usually a sign of connectivity or permission problems and must be investigated immediately. The following are the possible causes:
All local domain controllers are down or considered inappropriate. For example, all domain controllers must be running Microsoft® Windows® 2000 Server Service Pack 3 (SP3) or a later version.
Network problems do not let the Exchange server contact the domain controllers.
There are permissions problems.
To resolve this error, do one or more of the following:
Look up the Lightweight Directory Access Protocol (LDAP) error code specified in the event description. To do this, use Microsoft Knowledge Base article 218185, Microsoft LDAP Error Codes. Use the information in that article to learn more about the cause and resolution to this error.
Make sure that local domain controllers are reachable and running by doing one or more of the following:
Use the Ping or PathPing command-line tools to test basic connectivity. Use Ping to isolate network hardware problems and incompatible configurations. Use PathPing to detect packet loss over multiple-hop trips. For more information, see Microsoft Knowledge Base article 325487, How to troubleshoot network connectivity problems.
Run the Dcdiag command line tool to test domain controller health. To do this, run dcdiag /s:<Domain Controller Name> at a command prompt on the Exchange Server. Use the output of Dcdiag to discover the root cause of any failures or warnings that it reports. For more information, see Dcdiag Overview at the Microsoft Windows Server TechCenter.
Look for accompanying events in the Application log. You may have to increase logging for MSExchangeADAccess or MSExchange Topology performance objects to see these additional events.
If you are not already doing so, consider running the tools that Microsoft Exchange offers to help administrators analyze and troubleshoot their Exchange environment. These tools can help you make sure that your configuration is in line with Microsoft best practices. They can also help you identify and resolve performance issues, improve mail flow, and better manage disaster recovery scenarios. Go to the Toolbox node of the Exchange Management Console to run these tools now. For more information about these tools, see Toolbox in the Exchange Server 2007 Help.