Domain Controllers not Synchronizing

These are some basic steps that you can take when troubleshooting why Domain Controllers are not synchronizing.

1. Check Network Connectivity: Ensure that the domain controllers are connected to the network and can communicate with each other.
2. Check DNS Settings: Domain Name System (DNS) problems can cause Active Directory replication to fail¹. Make sure your DNS settings are correct.
3. Check Security Settings: Security problems, such as incorrect permissions, can also cause replication issues.
4. Use Diagnostic Tools: Tools like dcdiag and repadmin can help diagnose Active Directory issues. You can use these tools to check the replication status and identify any errors.
5. Check for Tombstoned DC: If a domain controller is not replicating, it may be tombstoned. You may need to demote the domain controller, transfer any FSMO roles, and then promote it again.
6. Use Microsoft Support Tools: Microsoft provides several tools to help troubleshoot Active Directory issues, such as the Active Directory Replication Status Tool and the Microsoft Support and Recovery Assistant tool.
7. Check SYSVOL: Perform a Non-Authoritative Sync of SYSVOL data using the File Replication Service (FRS).