2.1.2.3. Design for Azure AD Connect

💡 First Principle: A resilient and reliable synchronization service is the critical link for maintaining a consistent and up-to-date hybrid identity, ensuring seamless access to resources across both on-premises and cloud environments.

Scenario: You are designing the hybrid identity solution for an organization with an on-premises Active Directory. They need to ensure that user and group synchronizations to Azure AD are highly available and resilient to server failures.

Azure AD Connect is a Microsoft tool designed to connect your on-premises identity infrastructure with Microsoft Azure Active Directory.

Key Components and Functionalities:

• Synchronization Services: The engine that synchronizes directory objects and selected attributes (e.g., username, email, password hashes) from on-premises AD to Azure AD, maintaining identity consistency.
• Authentication Options: Azure AD Connect supports three authentication methods:
  • Password Hash Synchronization (PHS): Simplest, syncs password hashes.
  • Pass-through Authentication (PTA): Authenticates users against on-premises AD in real-time.
  • Federation with AD FS (Active Directory Federation Services): For advanced scenarios like smart card authentication.
• Health Monitoring: Azure AD Connect Health provides monitoring and alerting for synchronization services and AD FS, enabling proactive issue detection and resolution.

Designing for High Availability and Disaster Recovery:

• Staging Mode: Deploy a secondary Azure AD Connect server in staging mode. It synchronizes but does not export changes to Azure AD until activated, allowing rapid failover if the primary server fails.
• SQL Server Backend: Use a highly available SQL Server (e.g., Always On Availability Groups) for the synchronization database to eliminate single points of failure.

⚠️ Common Pitfall: Treating the Azure AD Connect server as a non-critical component. A failure of this server can halt all identity synchronization, leading to outdated group memberships and provisioning issues for new users.

Key Trade-Offs:

• Simplicity (LocalDB) vs. High Availability (Full SQL): The default Azure AD Connect installation uses a local SQL Express database, which is a single point of failure. For high availability, using a full, external SQL Server (with its own HA configuration) is required but adds complexity and cost.

Practical Implementation: Conceptual Failover Process

1. Primary Azure AD Connect server fails.
2. Monitoring (e.g., Azure AD Connect Health) alerts administrators.
3. Administrator takes the secondary server out of staging mode.
4. The secondary server becomes active and starts exporting changes to Azure AD.
5. Identity synchronization resumes.

Reflection Question: How does designing for Azure AD Connect (using staging mode for high availability and a highly available SQL Server backend) fundamentally ensure resilient, secure, and reliable hybrid identity synchronization, supporting seamless access to both cloud and on-premises resources?