Troubleshooting Azure AD Connect: Common Issues and Solutions

Your go-to guide for resolving frequent challenges with Azure AD Connect synchronization.

By: Alex Johnson Published: October 26, 2023 Category: Azure Active Directory, Hybrid Identity

Azure AD Connect is the backbone of hybrid identity, synchronizing on-premises Active Directory objects to Azure Active Directory. While generally robust, occasional issues can arise, leading to sync errors or unexpected behavior. This post aims to provide practical solutions for the most common problems you might encounter.

Understanding Synchronization Errors

The first step in troubleshooting is understanding the error messages. Azure AD Connect provides a Synchronization Service Manager tool that is invaluable for diagnosing issues.

Common Error Types:

  • Attribute-based errors: Often caused by invalid characters, incorrect formatting, or missing mandatory attributes.
  • Object-based errors: Typically related to duplicate attributes (like UPN or proxyAddresses) or objects in a pending state.
  • Connector Space errors: Occur when there's a problem connecting to or reading from either the on-premises AD or Azure AD connectors.
Tip: Always check the Synchronization Service Manager for detailed error information. Look for entries marked with a red X.

Issue 1: Synchronization Errors - Duplicate Attribute Values

One of the most frequent errors involves duplicate attribute values, such as multiple users sharing the same proxyAddresses or userPrincipalName. Azure AD requires unique values for these attributes.

Solution:

1. Identify the duplicate: Use the Synchronization Service Manager to pinpoint the attribute and the conflicting values.

2. Locate affected objects: Search your on-premises Active Directory for all objects that share the problematic attribute value.

3. Correct the attribute:

  • If it's a proxyAddresses issue, you can either remove the duplicate from one of the objects or assign a new, unique address.
  • For userPrincipalName (UPN) conflicts, you may need to update the UPN on one of the objects to a different domain suffix or a unique value. Ensure the UPN format is correct (e.g., `user@yourdomain.com`).

4. Resynchronize: After making corrections, run a full synchronization cycle.

# Example of identifying duplicate proxyAddresses in PowerShell (on-prem AD)
Get-ADUser -Filter * -Properties proxyAddresses | Where-Object {$_.proxyAddresses -ne ""} | Group-Object {$_.proxyAddresses} | Where-Object {$_.Count -gt 1} | Select-Object Name, Count

Issue 2: Objects Not Synchronizing

Sometimes, legitimate users or groups simply don't appear in Azure AD.

Possible Causes and Solutions:

  • Filtering: Check your Azure AD Connect configuration for any organizational unit (OU) filters or attribute-based filters that might be excluding the object.

    Solution: Adjust the filtering settings in the Azure AD Connect wizard if the object should be included.

  • Account disabled/deleted: Ensure the user account in on-premises AD is enabled and not marked for deletion.

    Solution: Re-enable the account or restore it from the AD recycle bin if necessary.

  • In-scope attribute: If you're using attribute-based filtering, ensure the object has the required attribute set to a value that is in scope.

    Solution: Add or modify the attribute value on the on-premises object.

Issue 3: Password Hash Synchronization (PHS) Failures

If users are unable to log in to Azure AD with their on-premises credentials, PHS might be the culprit.

Common Causes and Troubleshooting:

  • Event Log Errors: Check the Windows Event Viewer on the Azure AD Connect server for errors related to "Password Synchronization."
  • Permissions: The service account used by Azure AD Connect needs appropriate permissions to read password hashes from on-premises AD.

    Solution: Verify the permissions of the Azure AD Connect service account. It typically requires read access to the msDS-User-Account-Control-Computed attribute.

  • Firewall Issues: Ensure that the Azure AD Connect server can communicate with Azure AD endpoints over the necessary ports (usually port 443 for HTTPS).

    Solution: Consult your network team to confirm firewall rules allow the required outbound connections.

  • Stale Credentials: The credentials used by the Azure AD Connect service might have expired or been changed.

    Solution: Re-run the Azure AD Connect wizard and provide updated credentials if prompted, or update the service account password.

Important: For PHS, ensure that the ms-DS-ConsistencyGuid attribute is synchronized if you are using it as your source anchor.

Issue 4: Large Number of Pending Exports

Seeing a high number of "pending export" operations can indicate a backlog or a problem with the connection to Azure AD.

Troubleshooting Steps:

  • Check Azure AD Service Health: Ensure there are no ongoing incidents affecting Azure AD services.
  • Review Connector Space: Examine the connector space in the Synchronization Service Manager for any unusual objects or errors.
  • Network Latency: High network latency between your Azure AD Connect server and Azure AD can slow down exports.
  • Resource Utilization: Monitor the CPU and memory usage on the Azure AD Connect server. High utilization can impact performance.

Best Practices for Smooth Synchronization

  • Regularly Monitor: Use the Synchronization Service Manager and Azure AD Connect Health to keep an eye on synchronization status.
  • Document Changes: Keep a record of any changes made to your on-premises AD or Azure AD Connect configuration.
  • Test Thoroughly: After significant changes, perform test synchronizations before enabling them for production.
  • Keep Azure AD Connect Updated: Microsoft regularly releases updates with bug fixes and new features.

Troubleshooting Azure AD Connect issues often requires a systematic approach. By understanding common errors, utilizing the tools provided, and following best practices, you can maintain a healthy hybrid identity environment.