Exchange 2013 with two Mailbox servers in DAG. Recently one of the mailbox servers started showing the error below. The other mailbox server doesnt give this error in event logs.

Error
Process Microsoft.Exchange.Directory.TopologyService.exe (PID=2108) Forest DOMAIN.LOCAL. Topology discovery failed, error details 
No Minimal Required Number of Suitable Directory Servers Found in Forest DOMAIN.LOCAL Site Default-First-Site-Name and connected Sites..

MSExchangeADTopology
2142

The mailboxes are replicating fine still and all seem healthy.

Thank you

This might not be the case as it is happening with only one server out of two in the site but worth checking Managed Auditing and Security Log setting for Exchange Server goup...

The Exchange server does not have the Audit Security privilege on a Domain Controller - https://technet.microsoft.com/en-us/library/bb218747(v=exchg.80).aspx

Hi ABC,

Thank you for your question.

We make sure the service which is Microsoft Exchange Active Directory Topology is running on this mailbox.

If it is running and issue persist, we could refer to the following steps:

1.      Edit the Default Domain Controllers Policy in Group Policy.
2.        Computer Configuration->Windows Settings->Security Settings->User Rights Assignment->Mange auditing and security log
3.        Add Exchange Servers or Exchange Enterprise Servers to that policy.
4.        Run gpupdate /force on the domain controller and restart the Exchange Services

In addition, make sure IPv6 is enable on this server.

If there are any questions regarding this issue, please be free to let me know.

Best Regard,

Jim

Hi,

I am sorry that there are something which is missing, you could refer to the following path:

Computer Configuration->Windows Settings->Security Settings->Local Policies->User Rights Assignment->Mange auditing and security log

If there are any questions regarding this issue, please be free to let me know.

Best Regard,

Jim