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Monitoring Event Logs

When troubleshooting Active Directory replication issues, the Event Viewer is a critical tool for diagnosing failures. Replication problems often manifest as specific Event IDs in the System and Directory Services logs. These events provide detailed error messages, timestamps, and contextual information to pinpoint the root cause. This section focuses on identifying and interpreting key replication-related event IDs.

Key Event IDs for Replication Failures

Event ID 1358: "Replication Failure Between Domain Controllers"

  • Log: Directory Services
  • Description: Indicates a replication failure between two domain controllers (DCs). Common causes include network connectivity issues, DNS misconfigurations, or replication topology errors.
  • Example Command:
    Get-WinEvent -FilterHashtable @{LogName='Directory Services'; ID=1358} | Format-List
  • Action Steps:
  • Check the Event Details for the affected DC and replication partner.
  • Use repadmin /showrepl to verify replication status.
    Example:
    repadmin /showrepl * /verbose

Event ID 1393: "Replication Failure Due to Missing Data"

  • Log: Directory Services
  • Description: Occurs when a DC fails to replicate because the source DC lacks the required data (e.g., due to a partial or failed replication cycle). Often linked to Event ID 1358.
  • Example Command:
    Get-WinEvent -FilterHashtable @{LogName='Directory Services'; ID=1393} | Format-List
  • Action Steps:
  • Inspect the Event Details for the missing data type (e.g., "NTDS Settings").
  • Run dcdiag /c to check for inconsistencies in the directory.

Event ID 1375: "Replication Latency"

  • Log: System
  • Description: Indicates delayed replication between DCs, often due to network bandwidth issues or misconfigured replication intervals.
  • Example Command:
    Get-WinEvent -FilterHashtable @{LogName='System'; ID=1375} | Format-List
  • Action Steps:
  • Use repadmin /showrepl to check replication latency.
  • Adjust Replication Frequency settings in AD Sites and Services if necessary.

Event ID 1385: "Replication Delayed"

  • Log: System
  • Description: Suggests replication was delayed due to resource constraints (e.g., CPU, memory) on the DC.
  • Example Command:
    Get-WinEvent -FilterHashtable @{LogName='System'; ID=1385} | Format-List
  • Action Steps:
  • Monitor DC performance using Performance Monitor.
  • Ensure sufficient resources are allocated to the DC.

Additional Diagnostic Tools

  • repadmin /showrepl: Displays replication status across all DCs.
  • dcdiag: Validates directory service functionality and replication health.
  • ntdsutil: Analyzes replication metadata and logs.

Key takeaways

  • Monitor Event IDs 1358, 1393, 1375, and 1385 in the System and Directory Services logs for replication failures.
  • Use repadmin and dcdiag to correlate event details with replication health.
  • Combine event analysis with performance monitoring to address resource-related delays.
  • Regularly check DNS resolution and network connectivity between DCs to prevent replication errors.
  • Always validate event details in the Event Viewer before taking corrective action.