This event indicates that topology discovery determined that there are no suitable domain controllers in the local site or adjacent sites.

This can cause services startup failure or halting of mail flow and interruption of address book services. This problem should be investigated immediately.

This event may be logged if the following conditions are true:

• Network connectivity issues may be preventing communication with the global catalog server.
  
  
• The Exchange server may be pointing to the wrong DNS servers.
  
  
• DNS may be configured incorrectly or the configured DNS servers may be down and not reachable.
  
  
• Permission problems exist.
  
  

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

• Check the Application log for related events. The detail in other MSExchange ADAccess events and other events may help determine the root cause of this warning. Increase diagnostic logging for the MSExchange ADAccess\Topology category to Lowest or higher. For detailed information about how to increase logging, see Manage Diagnostic Logging Levels.
  
  
• If MSExchangeADAccess Event ID 2080 is logged, suitable global catalogs may not be present when initial topology discovery completes. Review that event to determine which domain controllers have been contacted and if they are not suitable for any reasons. Correct any problems as indicated by the event description. For more information, see Microsoft Knowledge Base article 316300, Event ID 2080 from MSExchangeDSAccess.
  
  
• If MSExchangeADAccess Event ID 2070 is logged, global catalog may be down or is unreachable. Review the event for more information about why each domain controller is not suitable. ADAccess found no suitable global catalogs when initial topology discovery was completed.
  
  
• 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.
  
  

For more information about the Get-EventLogLevel and Set-EventLogLevel diagnostic logging cmdlets, see the following topics:

• get-eventloglevel
  
  
• Set-EventLogLevel
  
  

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.