How to Resolve Active Directory Replication Errors

Introduction

Replication in Active Directory Domain Services (AD DS) is crucial to ensure data consistency across an environment. However, various issues can arise, such as DNS errors, RPC issues, or even topology problems, disrupting normal operations. In this article, we will examine the necessary steps to diagnose and fix Active Directory replication errors using tools such as repadmin, dcdiag, and PowerShell.

Identifying Replication Errors in Active Directory

The first step in resolving a replication error is to collect evidence and identify the scope of the problem. Here are the key steps:

1repadmin /replsummary

1mkdir C:\Temp\ADReplication
2repadmin /showrepl * /csv > C:\Temp\ADReplication\showrepl.csv
3dcdiag /e /test:replications /v > C:\Temp\ADReplication\dcdiag-replications.txt

Decoding Common Error Codes

Error codes in Active Directory provide clues about what needs to be fixed. Here is a table to guide you:

Resolving Error 1722: RPC Server Unreachable

An error 1722 indicates that the destination domain controller cannot establish an RPC connection with the source. Run the following tests to verify connectivity:

1Resolve-DnsName DC2.contoso.com
2Test-NetConnection DC2.contoso.com -Port 135

1portqry -n DC2.contoso.com -e 135
2portqry -n DC2.contoso.com -p tcp -r 49152:65535

Overcoming Error 2087: DNS Lookup Failure

Error 2087 typically occurs when the destination domain controller cannot resolve the DNS records necessary for replication. Follow these steps:

Step 1: Resolve GUID CNAME

Use the GUID of the source controller to test DNS records:

1Resolve-DnsName $SourceGuid._msdcs.contoso.com -Type CNAME
2Resolve-DnsName DC2.contoso.com -Type A

Step 2: Re-register Dynamic Records

Restart Netlogon to force re-registration of DNS records:

1Invoke-Command -ComputerName DC2 -ScriptBlock {
2    Restart-Service -Name Netlogon
3    ipconfig /registerdns
4}

Step 3: Eliminate Stale Sources

If the problem persists with an invalid controller, perform metadata cleanup with ntdsutil. Consult Microsoft documentation to perform this step.

Proactive Replication Monitoring

To minimize interruptions, set up a daily task to monitor replication:

1$Path = "C:\Reports\ADReplication"
2New-Item -ItemType Directory -Path $Path -Force | Out-Null
3 
4repadmin /showrepl * /csv > "C:\Reports\ADReplication\showrepl-(Get-Date -Format yyyyMMdd).csv"

Set up alerts for any desynchronization or delay detected in CSV snapshots.

Conclusion

Resolving replication issues in Active Directory involves identifying the problem layer, capturing detailed evidence, and following a systematic procedure. Always validate results before applying permanent solutions. Make sure to document your fixes to benefit from past events.