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Microsoft Entra Connect

Microsoft Entra Connect (formerly Azure AD Connect) is an on-premises Microsoft application designed to synchronize on-premises directory services, such as , with (formerly Azure Active Directory) to enable hybrid identity management across cloud and on-premises environments. Its primary purpose is to provide organizations with a unified identity for users, allowing seamless access to both local and cloud resources while enhancing productivity, security, and compliance in hybrid setups. Key features of Entra Connect include password hash synchronization, which replicates on-premises password hashes to for consistent authentication; pass-through authentication, enabling users to sign in to cloud services using the same passwords without requiring federated infrastructure; and integration with federation services like (AD FS) for advanced scenarios. It also supports comprehensive synchronization of user, group, and device data between directories, along with Microsoft Entra Connect for real-time monitoring and troubleshooting of sync operations and agent health. Microsoft Entra Connect evolved from earlier synchronization tools like DirSync and Azure AD Sync, serving as their successor to address growing needs. Version 1 of the tool was retired on August 31, 2022, with recommending upgrades to version 2, which incorporates updated components and ongoing enhancements while maintaining core functionality. Looking forward, is promoting Microsoft Entra Cloud Sync as a lightweight, cloud-based alternative to replace traditional on-premises sync agents for simpler deployments.

Overview

History and Rebranding

Microsoft Entra Connect originated from earlier tools designed to synchronize on-premises with cloud-based services. Its predecessor, DirSync, was introduced in 2011 primarily to enable between on-premises and Office 365, facilitating directory for scenarios. In September 2014, released AD Sync as an enhanced tool, expanding beyond to support broader hybrid , including password hash across multiple forests. This marked a shift toward comprehensive hybrid management, emphasizing seamless integration between on-premises environments and ( AD). Azure AD Sync evolved into Azure AD Connect with the release of version 1.0 in June 2015, introducing a unified for configuration and support for advanced features like seamless . Key milestones followed: version 1.1.371.0 in December 2016 introduced Pass-through Authentication, allowing direct validation of user credentials against on-premises domain controllers without storing hashes in the . In , Microsoft launched the provisioning agent (now part of Microsoft Entra Cloud Sync) in general availability, enabling lightweight, agent-based for scenarios with multiple forests or restricted connectivity. In July 2023, as part of a broader of Microsoft's portfolio, AD was renamed , and AD Connect became to align with the suite focused on secure access and hybrid . This did not alter core functionality but unified terminology across products. Recent developments in 2025 include hardening enhancements effective April 7, requiring upgrades to 2.4.18.0 or later to address security improvements in authentication and processes, preventing potential disruptions. In September 2025, released a dedicated first-party resource application in general availability, simplifying to for both Sync and Cloud Sync deployments. In October 2025, announced general availability for converting the Source of Authority of synced on-premises groups to cloud groups using Connect Sync or Cloud Sync, along with a public preview for cloud-managed remote mailboxes to support gradual reduction of on-premises dependencies.

Core Purpose and Functionality

Microsoft Entra Connect serves as an on-premises synchronization tool designed to integrate on-premises (AD) with , enabling organizations to manage hybrid identities across both environments. Its primary function is the bidirectional synchronization of directory objects, including users, groups, and devices, between an on-premises AD and a cloud-based tenant. This synchronization ensures that identity data remains consistent, allowing users to access resources seamlessly using the same credentials, while also supporting the import of password hashes to facilitate secure authentication without requiring users to maintain separate passwords. In the context of hybrid identity management, Microsoft Entra Connect facilitates key capabilities such as single sign-on (SSO), password hash synchronization, pass-through authentication, and integration with federation services like Active Directory Federation Services (AD FS). It also supports device writeback, which allows cloud-registered devices to be synchronized back to on-premises AD for centralized management. These features enable organizations to extend on-premises identity infrastructure to the cloud, supporting scenarios where users access both local applications and cloud services like without compromising security or user experience. The tool supports various deployment topologies, including single forest/single tenant configurations for straightforward environments, multiple forests consolidated into a single tenant for complex organizations, and staged rollouts to test in production without disrupting existing setups. Prerequisites for implementation include an operational on-premises environment, a provisioned tenant, and a SQL Server instance—either the bundled SQL Server Express LocalDB for smaller deployments or a full SQL Server for larger-scale operations—to store metadata. At a high level, the of Entra Connect revolves around its synchronization engine, which comprises connectors for interfacing with and , a provisioning component to handle object creation and updates, and a that serves as a centralized for normalized data from disparate sources. This engine processes changes delta-style, exporting updates to both directories to maintain synchronization without full rescans, thereby optimizing in hybrid setups. Evolving from earlier tools like DirSync, Entra Connect provides a more robust framework for modern hybrid needs.

Installation and Setup

Express Configuration

The Express Configuration option in Entra Connect provides a streamlined, wizard-based installation process designed for straightforward setups in single-forest Domain Services (AD DS) environments. This automated approach uses predefined rules to enable common features such as user and group , typically with password hash (PHS) as the default authentication method. It is particularly suited for organizations seeking a quick deployment without extensive customization, assuming a standard topology where Entra Connect is installed on a dedicated member server. To begin the setup, administrators download the Entra Connect installer () from the official portal and run it on a supported with local administrator privileges. The launches upon execution, prompting agreement to the terms, followed by selection of the "Use express settings" option. Next, users in with a Hybrid Identity Administrator account for , providing global administrator credentials to authorize the connection. Enterprise Administrator credentials for the AD DS forest are then entered to grant necessary permissions for reading and writing objects. The verifies the provided domains and proceeds to , which includes enabling PHS by default and optionally configuring hybrid deployment if selected. Administrators can choose to delay the initial cycle to allow for post-install adjustments, such as basic filtering, before completing the process by signing out and back in to access management tools. By default, Express Configuration synchronizes all users, groups, and contacts from a single forest without requiring manual organizational unit () selection, applying basic filtering to exclude built-in and system groups for optimal performance. It relies on the included LocalDB for the synchronization database, eliminating the need for a separate SQL instance in simple deployments. This setup ensures seamless integration for standard scenarios, such as syncing user identities and group memberships to , while supporting features like device writeback if prerequisites are met. However, Express Configuration is limited to single-forest environments and does not support complex topologies, such as multiple forests or intricate filtering rules, making it unsuitable for advanced setups. It assumes the use of SQL Express, which may not scale for high-volume needs, and lacks options for custom methods beyond PHS during initial installation. Following installation, verification involves launching the Synchronization Service Manager tool, accessible after signing out and back in, to review the initial synchronization status, export operations, and connector configurations. This step confirms that the full import and sync cycles have completed successfully, with logs indicating any errors in object synchronization from AD DS to .

Custom Configuration

Custom configuration of Entra Connect is utilized in complex deployments, such as multi- environments, scenarios requiring filtered , or those involving attribute mappings, where the automated express settings cannot accommodate specific organizational needs. This approach allows administrators to tailor the synchronization engine to precise requirements, ensuring only relevant objects and attributes are processed while supporting advanced topologies like account-resource forest separations. In multi-forest setups, for instance, all forests must be accessible from a single domain-joined Entra Connect Sync server, with user consolidation achieved through matching attributes such as the primary SMTP address or ObjectSID to represent each user uniquely in . Prior to initiating a custom installation, administrators must perform prerequisite checks, including verifying that the Active Directory schema version is Windows Server 2003 or later, enabling the Recycle Bin (recommended), and ensuring domain controllers are writable. The server hosting Microsoft Entra Connect must run , 2019, or 2022 (Windows Server 2025 not supported due to compatibility issues) with the full , .NET Framework 4.6.2 or later, and execution policy set to RemoteSigned. Hardware specifications scale with the number of synchronized objects, as outlined below:
Objects in ADCPURAMHard Drive
<10,0001.6 GHz6 GB70 GB
10,000–50,0001.6 GHz6 GB70 GB
50,000–100,0001.6 GHz16 GB100 GB
100,000–300,0001.6 GHz32 GB300 GB
300,000–600,0001.6 GHz32 GB450 GB
>600,0001.6 GHz32 GB500 GB
For environments exceeding 100,000 objects, a full SQL Server instance is required instead of the default LocalDB for optimal performance. Connectivity to on-premises Active Directory and Microsoft Entra endpoints must be established, with TLS 1.2 enforced, and appropriate accounts—such as a Global Administrator or Hybrid Identity Administrator—prepared with necessary permissions. The custom installation process begins by launching the Entra Connect wizard and selecting the "Customize" option, followed by configuring user sign-in methods (e.g., password hash synchronization or ) and connecting to on-premises directories by specifying names and enterprise administrator credentials. Optional features like password writeback or device writeback can be enabled, and the installer provides choices for staging mode or SQL Server usage during the database configuration step. For SQL integration in large-scale environments, administrators can connect to an existing full SQL Server instance (SQL Server 2022) by providing the server name, instance, and , using either SQL with sysadmin privileges or Windows ; this supports by allowing database restoration from backups to resume synchronization without a full resync, provided the sync state is within three weeks. Schema extensions for are automatically applied during installation if needed. Key custom elements include Organizational Unit (OU) filtering, which restricts synchronization to selected domains and OUs during the directory connection phase, ensuring essential OUs like those containing service accounts remain included to avoid disruptions. Attribute exclusions are managed through attribute filtering in the Entra app configuration, where specific attributes can be deselected to prevent , or via declarative provisioning rules that set the cloudFiltered attribute to true based on values like an extension attribute indicating "NoSync." For custom attribute mappings and metaverse join rules, the installation supports defining the sourceAnchor (typically immutableId derived from objectGUID) and alternateId for userPrincipalName matching, with post-installation adjustments possible using the Synchronization Rules Editor to create inbound and outbound rules for connector-to-metaverse joins, such as linking accounts across forests via msExchMasterAccountSID. Connector configurations are tailored during directory addition, allowing specification of credentials, filtering options, and details like full-mesh trusts for multi-forest scenarios. Staging server setup facilitates testing without impacting production synchronization; during custom installation, enable staging mode to allow the server to perform imports and delta synchronizations but halt exports to Microsoft Entra ID. This mode is ideal for validating configuration changes, such as filtered sync rules or custom mappings, by running full imports on connectors and using tools like csexport to preview export files before disabling staging mode on the primary server. In disaster recovery, the staging server can mirror the production configuration, including OU filters and attribute exclusions, to enable rapid failover by switching roles and resuming password synchronization from the last checkpoint.

Synchronization and Features

Synchronization Process

The synchronization process in Microsoft Entra Connect Sync facilitates the bidirectional flow of identity data between on-premises Domain Services (AD DS) and , ensuring consistency across hybrid environments. This process operates through a series of stages—import, , and —that handle object creation, updates, and deletions. Initially, a full synchronization cycle imports and exports all objects and attributes from connected data sources to establish a . Subsequent cycles use synchronization, which processes only changes detected since the last run, occurring every 30 minutes by default to minimize resource usage and network traffic. Central to this process are key components that manage data movement and integration. The AD Connector imports data from on-premises AD DS into a called the connector space, using anchors like objectGUID for object identification. The Entra ID Connector similarly handles imports from and exports to the cloud directory. The serves as a centralized repository that joins and aggregates identities from multiple connector spaces, creating a unified view without allowing direct modifications—changes propagate through attribute flows instead. Complementing these, the Provisioning Engine automates the creation or deletion of objects in target directories based on synchronization rules, ensuring that provisioning and deprovisioning actions align with business policies. The rules engine governs how attributes are transformed and flowed during synchronization, using declarative inbound and outbound rules to define mappings. Inbound rules update the from connector spaces, while outbound rules prepare data for export back to the connectors. For instance, the userPrincipalName attribute may be mapped from on-premises sources to the via these rules, with transformations applied to meet Entra ID requirements. These rules prioritize efficiency by evaluating precedence, such as favoring joins over new creations to avoid duplicates. Conflict resolution during synchronization employs a structured approach to handle discrepancies between data sources. The system first attempts a , linking a new object to an existing one in the using hard matches on anchors or soft matches on attributes like or proxyAddresses. If no match is found, it proceeds to create a new object, with join rules taking precedence to maintain . This mechanism supports soft-match joining on attributes such as to connect pre-existing with on-premises ones during initial setups. Monitoring the synchronization process relies on built-in tools for visibility and troubleshooting. The Synchronization Service Manager provides a graphical interface to view cycle status, inspect connector spaces, and review errors from recent runs. Event Viewer logs detailed events from the Microsoft Entra Connect Sync service, capturing import/export outcomes, rule executions, and any failures for diagnostic purposes. These tools enable administrators to track delta sync intervals and intervene if a full sync is needed after prolonged issues.

Authentication Options

Microsoft Entra Connect provides several authentication options to enable hybrid identity scenarios, allowing users to sign in to both on-premises and cloud-based applications using the same credentials. These options integrate on-premises (AD) with , supporting seamless (SSO) and policy enforcement. The primary methods include password hash synchronization, pass-through authentication, and , each suited to different organizational needs based on infrastructure, security requirements, and complexity. Password Hash Synchronization (PHS) synchronizes hashed passwords from on-premises to , enabling cloud without storing full passwords in the cloud. When a user signs in to a -integrated application, the service validates the password against the synchronized hash. This method requires no additional on-premises infrastructure beyond the Entra Connect server itself and supports features like Protection for risk-based . PHS is irreversible once enabled for a domain, converting it from federated to managed . Pass-through Authentication (PTA) deploys lightweight agents on on-premises Windows servers to validate user passwords directly against in real time during sign-in attempts. Unlike PHS, PTA does not store password hashes in , ensuring immediate enforcement of on-premises policies such as account lockouts, sign-in hours, or disabled status. Agents communicate outbound to over , with high availability achieved by installing multiple agents across domain controllers or member servers. PTA integrates with Seamless SSO for Kerberos-based on corporate networks and requires no inbound ports on the . Federation with (AD FS) enables SAML-based by establishing a trust relationship between on-premises AD FS and . Entra Connect simplifies setup by configuring the automatically during installation, converting domains to federated and redirecting authentication requests to the AD FS farm. This option supports advanced scenarios, including custom authentication logic, third-party (MFA), or claims-based . An AD FS deployment typically requires at least two federation servers and web application proxies for , along with a valid TLS/SSL certificate. Seamless SSO can be enabled alongside for access. Organizations select options based on factors such as deployment simplicity, posture, and existing . PHS is recommended for most scenarios due to its low maintenance and native support for Entra features, avoiding the need for additional servers. PTA suits environments requiring strict on-premises enforcement without overhead, offering a balance of and ease. with AD FS is ideal for complex setups with legacy investments or non- MFA needs, though it demands more resources and management. All options require synchronization prerequisites like domain-joined Entra Connect servers to function effectively.

Upgrades and Maintenance

Version History and Upgrades

Entra Connect underwent significant evolution following its rebranding from AD Connect in 2023, with version releases focusing on improved reliability, enhancements, and compatibility with modern standards. The progression of versions from 2.2 onward has emphasized hardening against vulnerabilities, expanding attribute support, and integrating new features like modern in public preview. Key releases are summarized in the following table, highlighting major updates and their release dates. As of November 15, 2025, versions with support ending on or before this date (e.g., all 2.3.x and 2.4.18.0, 2.4.21.0) are retired, requiring immediate upgrades to avoid disruptions. enforces a retirement policy providing 12 months of support after a newer version's release (effective March 15, 2023), with services halting entirely on September 30, 2026, for installations not upgraded to 2.5.79.0 or later.
VersionRelease DateSupport End DateKey Features and Changes
2.2.1.0June 19, 2023RetiredEnabled auto-upgrades for custom synchronization rules; introduced Agent Updater service for seamless maintenance; removed WebService Connector Config; improved accessibility; updated employeeType attribute flow.
2.2.8.0October 11, 2023RetiredAdded onPremisesObjectIdentifier attribute; upgraded to .NET Framework 4.7.1; fixed group deprovisioning issues; improved upgrade process.
2.3.2.0December 12, 2023April 30, 2025 (retired)Introduced application scaling for accessibility; decommissioned Group Writeback V2; updated SQL drivers and health agent to 4.5.2428.0 for better performance; fixed DSSO bug for Azure China.
2.3.6.0February 21, 2024April 30, 2025 (retired)Improved auto-upgrade detection for OS/.NET requirements.
2.3.8.0April 1, 2024April 30, 2025 (retired)Updated health agent to 4.5.2466.0 for endpoint discovery.
2.3.20.0July 15, 2024April 30, 2025 (retired)Mandated TLS 1.2 enforcement; enhanced Self-Service Password Reset (SSPR) handling; updated SQL drivers (ODBC 17.10.6, OLE DB 18.7.2); improved accessibility.
2.4.18.0October 7, 2024October 9, 2025 (retired)Added onPremisesObjectIdentifier synchronization rule; decommissioned schema validation and /enableldap switch; replaced MSOnline PowerShell references with Microsoft Graph API; requires .NET 4.7.2; removed password requirement for Microsoft Entra ID connection; introduced registry key for custom rule precedence; fixed various wizard and sync issues.
2.4.21.0October 9, 2024November 15, 2025 (retired)Resolved authentication issues with non-commercial clouds.
2.4.27.0November 14, 2024January 15, 2026Updated SQL drivers to OLE DB 18.7.4; improved PIM role verification; fixed AD FS command failures on non-ADFS servers.
2.4.129.0January 15, 2025March 27, 2026Fixed SSPR configuration removal; improved role validation with PIM; resolved AD FS federation errors.
2.4.131.0March 27, 2025May 26, 2026Removed SchUseStrongCrypto registry check; enabled for auto-upgrade until April 15, 2025.
2.5.3.0May 27, 2025July 31, 2026Introduced modern authentication support (public preview); updated Microsoft Entra Connect Health agent to version 4.5.2520.0; moved downloads to Azure portal; required admin credentials for staging mode/SSPR via PowerShell.
2.5.76.0July 31, 2025January 9, 2026Resolved child OU selection issues in multi-domain scenarios; fixed Azure MFA vs. ADFS MFA prompt; ensured auto-upgrade with missing agent identifiers; fixed DirSync status mismatch error. Auto-upgrade starts August 14, 2025, in phases.
2.5.79.0September 1, 2025N/A (current)Improved Application-Based Authentication setup with TPM-backed certificates; automatic certificate removal on failure; resolved FIPS-enabled server setup failures; fixed certificate auto-rotation status reporting; removed inappropriate admin audit events. Auto-upgrade starts September 4, 2025, in phases. Mandatory upgrade to this or later by September 30, 2026, to avoid service disruption.
All 1.x versions of the tool reached end of support on , 2022, due to reliance on retired components like SQL Server 2012, necessitating upgrades to version 2.x or later to maintain functionality. Upgrade paths vary by scenario, with in-place suitable for minor version updates on single servers handling fewer than 100,000 objects, while side-by-side (swing) migrations are recommended for major transitions, such as from 1.x to 2.x, or when involving significant configuration changes or operating system . In-place preserve most settings but may trigger full imports and , suspending delta syncs temporarily while password remains active. For custom configurations, side-by-side approaches allow testing on a server before switching roles. Compatibility requires or later, SQL Server 2012 SP4 or higher (with later versions preferred for security), .NET Framework 4.7.2, and TLS 1.2 enforcement across all components. Manual upgrade procedures begin with a full of the server configuration and database to mitigate risks. Administrators then download the latest . installer from the Entra Admin Center and run it on the target server, following the wizard prompts to apply updates; for custom SQL deployments, migration involves backing up and restoring the database if switching instances. Post-upgrade verification includes checking the Synchronization Service Manager for object counts and error-free cycles, reviewing event logs for issues, and confirming configuration integrity using built-in tools. Custom rules must be re-applied or exported/imported via if not preserved during the process.

Automatic Upgrade Mechanisms

Microsoft Entra Connect includes a built-in automatic designed to ensure seamless updates to without , provided the installation meets specific eligibility criteria. This feature is enabled by default for 1.1.105.0 and later, particularly those using Express settings or upgraded from DirSync, and it regularly checks for available updates via Microsoft Entra Connect Health. Eligibility further requires the use of SQL Express LocalDB, fewer than 100,000 objects in the , the default MSOL_AD service account, TLS 1.2 or higher, and no custom rules prior to 2.2.1.0; installations exceeding these parameters, such as those with custom SQL setups or large-scale deployments, are ineligible and necessitate manual upgrades. The upgrade process operates in the background to minimize disruption: it downloads the new version package after validating its , then installs it during a period of low activity, with upgrades staggered randomly after release to avoid widespread simultaneous impacts. If the fails—due to issues or other errors—the system automatically rolls back to the previous version, logging the event as "UpgradeFailedRollbackSuccess" in the Application event log. This mechanism applies only to minor version updates; major version transitions, such as from 1.x to 2.x, require manual intervention to ensure stability. In 2025, implemented phased automatic upgrades for version 2.5.76.0, beginning on August 14 and rolling out in stages to eligible installations, followed by version 2.5.79.0 starting September 4. Additionally, under the Lifecycle Policy, environments running versions 2.3.2.0, 2.3.6.0, 2.3.8.0, or 2.3.20.0 faced a mandatory upgrade deadline of April 30, 2025, to version 2.4.18.0 or later for compatibility with updated security features and the configuration wizard. Administrators can control the automatic upgrade feature using the PowerShell cmdlet Set-ADSyncAutoUpgrade -AutoUpgradeState Disabled to turn it off, or Enabled to reactivate it, with the current state queryable via Get-ADSyncAutoUpgrade. Upgrade notifications and status details, including event IDs 300-399, are recorded in the Windows Application event log under the "Microsoft Entra Connect Upgrade" source, allowing monitoring without reliance on the Microsoft Entra admin center. Limitations persist for non-standard configurations, such as custom SQL databases or those with disabled health data upload, where automatic upgrades are unavailable and manual processes must be followed per version prerequisites.

Advanced Usage and Integration

PowerShell Integration

Microsoft Entra Connect provides integration through dedicated modules that enable administrators to manage synchronization services, configure features, and automate tasks without relying on the graphical user interface. The primary module, ADSync, is installed automatically with Microsoft Entra Connect and offers cmdlets for controlling sync cycles and scheduler settings. An additional module, ADSyncTools, can be installed separately via the PowerShell Gallery using Install-Module -Name ADSyncTools to access advanced tools for object management and exports. Common cmdlets in the ADSync module include Get-ADSyncScheduler, which retrieves the current synchronization scheduler configuration, such as cycle status and intervals, allowing administrators to monitor ongoing operations. For initiating synchronization, Start-ADSyncSyncCycle triggers a delta or initial sync cycle, with parameters like -PolicyType Delta to specify the type, useful for testing changes without full exports. Feature toggles, such as enabling or disabling password hash synchronization, can be managed through related cmdlets like those in the sync service configuration, though direct toggles often integrate with broader setup scripts. Advanced scripting capabilities extend to custom rule exports and bulk operations via the ADSyncTools . For instance, Export-ADSyncToolsAadDisconnectors exports Microsoft Entra objects to format, facilitating analysis of unsynchronized items by attributes like UserPrincipalName or SourceAnchor, which supports custom rule development and validation. Bulk attribute updates are handled by cmdlets such as Set-ADSyncToolsMsDsConsistencyGuid, which applies source anchor changes to multiple objects in a single operation, ensuring consistency across hybrid environments. Key use cases for integration include automating staging mode tests, where scripts can toggle via registry modifications or integrated cmdlets to preview configurations without affecting syncs. Monitoring sync errors involves querying scheduler status with Get-ADSyncScheduler and reviewing run history through event logs or cycle statistics to detect failures proactively. Integration with Automation allows scheduling these scripts as runbooks, enabling unattended operations like periodic sync triggers or error reporting to . As of 2025, enhancements include new cmdlets for pass-through (PTA) agent management, such as Get-PassthroughAuthenticationEnablementStatus to check agent status and Disable-PassthroughAuthentication for configuration adjustments. For cloud sync configurations, the .CloudSync. module provides cmdlets like Connect-AADCloudSyncAzureAD for , Add-AADCloudSyncGMSA for group managed setup, and Add-AADCloudSyncADDomain for , streamlining provisioning deployments.
powershell
# Example: Trigger a delta sync cycle
Import-Module ADSync
Start-ADSyncSyncCycle -PolicyType Delta
These tools build on the core synchronization process by providing programmatic control, allowing for scalable hybrid identity management.

Troubleshooting and Best Practices

Common synchronization errors in Microsoft Entra Connect often include duplicate attributes, such as userPrincipalName or proxyAddresses, which can cause InvalidSoftMatch or AttributeValueMustBeUnique errors during the sync process. These arise from conflicting data in on-premises Active Directory (AD) and can be resolved by identifying and removing duplicates using AD tools before resyncing. Connectivity failures to Microsoft Entra ID typically manifest as export errors or authentication timeouts, often due to network restrictions or expired credentials for the Microsoft Entra connector account. For Pass-through Authentication (PTA), common issues include agents appearing offline (error code 80001), which prevents password validation, or timeouts connecting to AD (error code 80002 or 80007). Resolutions involve verifying agent status in the Microsoft Entra admin center, ensuring domain join and network reachability to AD, and reinstalling agents if necessary. Diagnostic tools play a crucial role in identifying root causes. The IdFix DirSync Error Remediation Tool scans on-premises AD for issues like duplicate or invalid attributes (e.g., proxyAddresses or userPrincipalName) prior to synchronization, allowing bulk corrections to prevent sync failures. For detailed logs, miisclient.exe (Synchronization Service Manager) provides access to operations, connectors, and data, enabling administrators to review sync cycles, export errors, and rule configurations directly. Additionally, Entra Connect offers object-level error reports updated every 30 minutes, categorizing issues like duplicate attributes or data mismatches with exportable details for remediation. Best practices emphasize proactive maintenance to ensure reliable deployments. Regular health checks via the Microsoft Entra admin center's Connect Health portal monitor sync , object changes, and for issues like failures or high resource usage, with steps provided for each . Secure agent deployment for involves using domain-joined servers with outbound access to required URLs and ports (e.g., TCP 443 to login.online.com), deploying multiple agents for to avoid single points of failure. Backup strategies for the configuration database (ADSync in SQL LocalDB or remote SQL) include regular using , avoiding third-party agents that may cause deadlocks, and backing up keys and rules separately to enable full restoration. Performance optimization is essential for large directories exceeding 100,000 objects. Implement scoping filters (e.g., or attribute-based) to reduce synced objects and minimize full sync cycles, which can take hours initially. For scale-out, deploy a staging in passive mode for or testing, ensuring only one active sync per tenant to avoid conflicts across forests. Tune sync intervals using (e.g., Set-ADSyncScheduler for delta sync every 30 minutes) to complete cycles within that window, preventing backlog in high-churn environments; use SSD storage for the SQL database to improve write performance. Security considerations focus on minimizing exposure through least-privilege principles. Use dedicated service accounts like the ADSync account (gMSA recommended for remote SQL) with permissions limited to Replicate Directory Changes and specific AD reads/writes, avoiding domain admin rights where possible. Post-2025 hardening updates require upgrading to version 2.5.79.0 or later by September 30, 2026, enforcing TLS 1.2 and .NET 4.7.2 to prevent sync failures from deprecated protocols. Monitor for unauthorized changes via Connect Health alerts on authentication failures or service stoppages, and rotate credentials regularly while auditing access to the sync server.

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