This Error event indicates that the 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, at least one domain controller must be running Windows Server 2003 Service Pack 1 (SP1) or later. For more information about Active Directory minimum requirements, see Exchange 2010 System Requirements.
  
  
• Network problems prevent the Exchange server from contacting the domain controllers.
  
  
• There are permissions problems.
  
  

To resolve this error, do one or more of the following:

• Verify at least one domain controller is running Windows Server 2003 SP1 or later.
  
  
• Look up the Lightweight Directory Access Protocol (LDAP) error code specified in the event description. To do this, refer to 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 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 Exchange tools created to help you analyze and troubleshoot your Exchange environment. These tools can help make sure that your configuration aligns with Microsoft best practices. They can also help you identify and resolve performance issues, improve mail flow, and better manage disaster recovery scenarios. To run these tools, go to the Toolbox node of the Exchange Management Console. To learn more about these tools, see Managing Tools in the Toolbox.