Active Directory replication troubleshooting guidance

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This article is designed to help get you started troubleshooting Active Directory replication issues.

Troubleshooting checklist

Use the following checklist to troubleshoot these replication issues:

  • The error and warning events in the Directory Service event log indicate the specific constraint that's causing replication failure on the source or destination domain controller. If the event message suggests steps for a solution, try the steps that are described in the event.

  • Diagnostic tools such as Repadmin also provide information that can help you resolve replication failures. To help monitor replication and diagnose errors, download and run the Microsoft Support and Recovery Assistant tool.

  • Rule out intentional disruptions or hardware failures.

  • In a scenario: A domain controller is built in a staging site. The domain controller is currently offline, and is waiting for its deployment in the final production site, a remote site such as a branch office.

    When another domain controller is trying to replica with the domain controller, it reports replication errors. You can account for such replication errors.

  • Replication problems might be caused by hardware failure.

  • Active Directory replication remote procedure calls (RPCs) occur dynamically over an available port through the RPC Endpoint Mapper (RPCSS) on port 135. Make sure that Windows Defender Firewall with Advanced Security and other firewalls are configured correctly to enable replication.

After you rule out intentional disconnections and hardware failures, the replication issues might have one of the following causes:

  • Network connectivity: The network connection might be unavailable, or network settings might not configured correctly.
  • Name resolution: DNS misconfigurations are a common cause of replication failures.
  • Replication engine: If intersite replication schedules are too short, replication queues might be too large to process in the time that is required by the outbound replication schedule. In this case, replication of some changes might be stalled indefinitely, or long enough to exceed the tombstone lifetime.
  • Replication topology: Domain controllers must have intersite links in Active Directory Domain Services (AD DS) that map to real wide area network (WAN) or virtual private network (VPN) connections. If you create objects in AD DS for the replication topology that aren't supported by the actual site topology of your network, replication that requires the misconfigured topology fails.
  • Authentication and authorization: Authentication and authorization problems cause "access denied" errors when a domain controller tries to connect to its replication partner.
  • Directory database store: The directory database might not be able to process transactions fast enough to keep up with replication time-outs.

Common solutions for Active Directory replication issues

  • Monitor replication health daily, or use Repadmin to retrieve replication status daily.
  • Try to resolve any reported failure in a timely manner by using the methods that are described in the event messages and this guide. If software is causing the problem, uninstall the software before you continue to try other solutions.
  • If the problem that is causing replication to fail can’t be resolved by any known methods, remove AD DS from the server, and then reinstall it. For more information about reinstalling AD DS, see Decommissioning a Domain Controller.
  • If AD DS can't be removed in a typical manner while the server is connected to the network, use one of the following methods to resolve the problem:
    • Force AD DS removal in Directory Services Restore Mode (DSRM), clean up server metadata, and then reinstall AD DS.
    • Reinstall the operating system, and rebuild the domain controller.

Common issues and solutions

Most replication problems are identified in the event messages that are logged in the Directory Service event log. Replication problems might also be identified in the form of error messages in the output of the repadmin /showrepl command.

Event ID 2042

Repadmin message:

The time since last replication with this server has exceeded the tombstone lifetime.

A domain controller has failed inbound replication with the named source domain controller long enough for a deletion to have been tombstoned, replicated, and garbage-collected from AD DS. See Active Directory replication Event ID 2042.

Event ID 1925

Repadmin message:

No inbound neighbors

If no items appear in the "Inbound Neighbors" section of the output that is generated by repadmin /showrepl, the domain controller wasn't able to establish replication links with another domain controller. See Active Directory replication Event ID 1925.

Error code 5

Repadmin message:

Access is denied.

A replication link exists between two domain controllers, but replication can’t be done correctly because of an authentication failure. See Active Directory replication fails with error 5: Access is denied.

Error code 49

Repadmin message:

LDAP Error 49.

The domain controller computer account might not be synchronized with the Key Distribution Center (KDC). Fix replication security issues.

Event ID 1925 and event ID 2087

Repadmin message:

Cannot open LDAP connection to local host.

The administration tool couldn't contact AD DS. See the following articles:

Event ID 1925, event ID 2087 and event ID 2088

Repadmin message:

Last attempt at <date - time> failed with the "Target account name is incorrect."

This problem can be related to connectivity, DNS, or authentication issues. If this error is a DNS error, the local domain controller couldn't resolve the globally unique identifier (GUID)-based DNS name of its replication partner. See the following articles:

Data collection

If you need assistance from Microsoft support, we recommend you collect the information by following the steps mentioned in Gather information by using TSS for Active Directory replication issues.