Symptoms
Assume that you have a large-scale deployment that contains hundreds of Microsoft Exchange servers. After you make changes in Active Directory Domain Services (AD DS), the CPU and network resources become intermittently overloaded on some domain controllers. For example, the issue may occur after you change the Active Directory site or subnet configurations. When this issue occurs, the LDAP Search Time performance counter on the affected Exchange servers has a value that is larger than expected.
Note You can check the CPU and network usage in Performance Monitor.
Additionally, if the domain controller has the intersite topology generator (ISTG) role, ISTG updates trigger each Exchange server to perform a complete topology discovery, and that causes this issue to occur every 15 minutes.
Cause
This issue occurs because multiple Exchange servers send many large LDAP queries at the same time, triggering a complete topology discovery for each query.
Resolution
To resolve this issue, install the following update:
2961522 Update Rollup 7 for Exchange Server 2010 Service Pack 3
Note This update can randomize the deferral time for Exchange to send out the LDAP queries of complete topology discovery.
Workaround
To work around this issue, use one of the following methods.
Method 1
Exclude the domain controller that has the ISTG role. To do this, run the following command in Exchange Management Shell (EMS):
Set-ExchangeServer -identity Server -StaticExcludedDomainControllers DomainController
Note If you want to remove the change that you have made and revert to the default behavior of Exchange, run the following command in EMS:
Set-ExchangeServer -identity Server-StaticExcludedDomainControllers:$null
Method 2
Increase the number of domain controllers in your organization. Then, each domain controller will be connected by a smaller number of Exchange servers. This results in a smaller load for each domain controller.
Status
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
More Information
For more information about the ISTG role, go to the following Microsoft website:
General information about KCC and topology generationFor more information about the Set-ExchangeServer cmdlet, go to the following Microsoft website:
