Replication between primary and additional domain controllers has failed: how should AD, DNS, time, and SYSVOL be checked?

Domain-controller replication failures affect accounts, passwords, GPOs, and sign-ins. Start with replication summaries and error codes, then verify DNS, sites, RPC, time, and DFSR.

1. Conclusion and scope

Before troubleshooting, collect the client and server versions, domain and site details, client DNS configuration, the domain controllers involved, the complete error text, relevant event logs, and recent AD, DNS or Group Policy changes. corp.example is a reserved example domain and does not represent a customer environment.

This issue involves Active Directory and Group Policy. Logs and configuration can often be collected remotely first. Bulk permission changes, switch-path work, production cutovers, and recovery drills should use a controlled implementation window.

2. Symptoms and business impact

• Capture the complete error text, event-log timestamp, and failed action rather than relying on a verbal description.
• Record the affected scope, first occurrence, reproducibility, and whether the result changes on another subnet.
• Domain-controller replication failures affect accounts, passwords, GPOs, and sign-ins. Start with replication summaries and error codes, then verify DNS, sites, RPC, time, and DFSR.

3. Likely causes and diagnostic checks

1. Use repadmin to review the replication summary, failing source, error code, site, connection object, and naming context.
2. Run dcdiag and focus on DNS, Advertising, Services, SysVolCheck, and NetLogons results.
3. Confirm every domain controller uses DNS that can resolve the AD zone, site-to-subnet mappings are correct, and cross-site routing plus dynamic RPC are permitted.
4. Verify consistent time zones and time sources across clients, domain controllers, and hypervisors to prevent Kerberos failures.
5. If replication problems coincide with inconsistent GPOs, verify SYSVOL and NETLOGON shares, DFSR events, and policy versions on each domain controller.
6. Across subnets, validate DNS, Kerberos, LDAP, SMB, RPC and the dynamic RPC range instead of testing a single port.

repadmin /replsummary
repadmin /showrepl * /errorsonly
dcdiag /test:dns /test:advertising /v

4. Remediation and controlled rollout

Start with read-only queries, configuration exports, and one-system validation. Once the root cause is confirmed, define the target scope, change window, and rollback method. For multiple computers, use a test OU and a small pilot group, export policy results, and roll out in stages only after side effects are excluded.

• Verify consistent time zones and time sources across clients, domain controllers, and hypervisors to prevent Kerberos failures.
• If replication problems coincide with inconsistent GPOs, verify SYSVOL and NETLOGON shares, DFSR events, and policy versions on each domain controller.
• Across subnets, validate DNS, Kerberos, LDAP, SMB, RPC and the dynamic RPC range instead of testing a single port.

5. Validation, rollback and common mistakes

Do not stop when the service works once. Revalidate with the user workflow, logs, a restart or fresh sign-in, another network location where relevant, and the next policy or backup cycle.

Validation and rollback checks

• Change one variable at a time and export the current configuration before making changes.
• Verify consistent time zones and time sources across clients, domain controllers, and hypervisors to prevent Kerberos failures.
• Confirm AD and SYSVOL replication between domain controllers and verify that the contacted controller has the expected policy version.

Common mistakes to avoid

• Using public DNS or permanent hosts-file entries for domain controllers.
• Removing a computer from the domain before confirming local administrator access.
• Linking a new GPO to the entire domain without a pilot group.