Exchange 2016: – EventID 2193, MSExchange ADAccess

In my test environment, I have multiple versions of Exchange, Exchange 2010, 2013 and 2016.

Exchange 2010 and 2013 log event ID 2080 for the Topology with no errors. All Domain controllers are visible and can be contacted, however a strange error seems to be happening on the Exchange 2016 Servers.

Event ID 2080 is logged but reporting Domain controllers are not available, after each 15 minute check, they change, the ones that were reporting as down are now reporting healthy again and on the Exchange 2016 Server Event ID 2193 is logged as shown below with errors contacting the domain controllers on port 389 and 3268:

What is strange here, after a reboot the Topology shows healthy without the above EventID being logged. However after an hour it just starts the same cycle.

Steps to check LDAP:

  • Ran a DCDiag and no errors reported.
  • Checked AD Sites and Services and nothing out the ordinary showing.
  • Ran an advanced PowerShell script to check the domain controllers and no issues reported.
  • Rebooted domain controllers.
  • Installed the follow-up patch on the Domain controllers that had the affected July patch.
  • Ran ADInsight and could not see anything strange.
  • Changed DNS on the Exchange servers.

Even though the above is reported, Exchange is still running without an error, EMS launches without error.

I have sent the above to the Product Team to advise if this is a bug in Exchange 2016 CU10. Will update my post once they have responded and if I can post the fix.

Hope it helps.

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