How to Troubleshoot Active Directory Replication Failures Step-by-Step

Windows Server • Active Directory • Replication • Troubleshooting

Active Directory replication issues are among the most critical problems in enterprise environments. When replication fails, password changes do not propagate, Group Policy becomes inconsistent, and authentication errors begin to appear across sites.

Reality: Most replication problems are caused by DNS misconfiguration, firewall issues, time skew, or broken secure channels.

Common Symptoms

Password changes not recognized on other DCs
GPO inconsistencies between sites
Event ID 1311, 1566, 1865
Kerberos errors
Users authenticating only on specific DCs

Step 1 – Check Replication Summary

Run on any Domain Controller:

repadmin /replsummary

This provides: - Failing DCs - Error percentages - Time since last successful replication If you see high failure counts, continue deeper. ---

Step 2 – Detailed Replication Status

repadmin /showrepl

Look for: - RPC errors - Access denied - Naming context failures - Long replication intervals ---

Step 3 – Run Domain Controller Diagnostics

dcdiag /v

Focus on: - Connectivity - Advertising - NetLogons - DNS tests If DNS test fails → replication will fail. ---

Step 4 – Check Time Synchronization

Kerberos requires time accuracy. Check:

w32tm /query /status

Time difference above 5 minutes can break authentication and replication. ---

Step 5 – Force Replication (If Needed)

repadmin /syncall /AdeP

This forces replication across all partitions and sites. ---

Step 6 – Verify DNS Resolution Between DCs

Test name resolution:

nslookup dc02.yourdomain.local
ping dc02

If DNS fails → replication fails. ---

Step 7 – Check Firewall & Ports

Replication requires: - TCP 135 (RPC) - Dynamic RPC ports - LDAP 389 - Kerberos 88 Blocked ports are a common cause in segmented networks. ---

Common Root Causes

Incorrect DNS configuration
Public DNS on domain controllers
Broken secure channel
Time skew
Firewall blocking RPC
Lingering objects after improper DC removal

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Best Practice Prevention Strategy

✔ Internal DNS only on DCs ✔ Monitor replication health weekly ✔ Use AD-integrated zones ✔ Proper site/subnet configuration ✔ Remove decommissioned DCs cleanly ---

Conclusion

Replication failures rarely fix themselves. A structured troubleshooting approach using repadmin, dcdiag, DNS verification and time synchronization checks can quickly isolate the root cause. In enterprise environments, proactive monitoring of replication health is far more effective than reactive troubleshooting.