Azure AD Cross-Tenant Synchronization (CTS) Step-by-Step Guide

 Azure AD Cross-Tenant Synchronization (CTS) Step-by-Step Guide


Azure Active Directory (Azure AD) Cross-Tenant Synchronization (CTS) enables organizations to synchronize and manage user identities across multiple Azure AD tenants. This feature is particularly useful when an organization wants to share resources or collaborate between different Azure AD tenants but does not want to combine or merge those tenants.

Here's a step-by-step guide to setting up Azure AD Cross-Tenant Synchronization:

Pre-requisites:

Before starting the configuration, ensure you have the following:

  1. Admin Access: You must have global admin or tenant admin roles in both the source and target Azure AD tenants.
  2. Azure AD Connect: Ensure you have the correct setup of Azure AD Connect in place if you're using on-premise Active Directory for synchronization.

Step 1: Prerequisites for Cross-Tenant Synchronization

  • Azure AD tenants: You need at least two Azure AD tenants — one for the source and one for the target.
  • Global Admin Permissions: You'll need Global Admin permissions for both tenants (source and destination).
  • Licensing: Cross-tenant synchronization may require Azure AD Premium P1 or P2 licenses for both the source and destination tenants.

Step 2: Configure the Source Tenant (Start the Setup)

  1. Sign in to Azure Portal:

    • Go to Azure Portal and sign in with your admin credentials for the source tenant.

  2. Navigate to Azure Active Directory:

    • In the Azure portal, search for Azure Active Directory and click to open.

  3. Enable External Identities (if required):

    • In the Azure AD dashboard, navigate to External Identities → Cross-tenant access settings. Here, you'll configure the relationship between tenants.

  4. Configure Cross-Tenant Access Settings:

    • Under External Identities, you’ll see options to configure the Cross-tenant access settings.
    • Here, you can configure whether you want users from other Azure AD tenants to access resources in your tenant.
    • You can also specify whether these users will be granted direct access (with permissions) or if you will use a more restrictive sharing model.

Step 3: Configure the Target Tenant

  1. Sign in to the Target Tenant:

    • In the Azure portal, sign in with the admin credentials for the target Azure AD tenant (the one receiving users).

  2. Set Up Cross-Tenant Access:

    • Again, go to Azure Active Directory → External Identities → Cross-tenant access settings.
    • Configure the same settings as for the source tenant, ensuring that the relationship between the source and the target tenant is correctly set.

  3. Configure User Permissions for Access:

    • Define which users/groups from the source tenant can access resources in the target tenant. This could include setting up user-to-user access or group-based access for specific applications or resources.
    • Consent for cross-tenant access: Depending on the configurations, users may be required to give consent before their identities can be shared.

Step 4: Create Cross-Tenant Access Policy

  1. Access the "Cross-tenant Access Settings" in the Source Tenant:

    • Go back to the Cross-tenant access settings page in the source tenant.
    • Here, you will create policies that control how users from one tenant are allowed to interact with resources in another tenant. For example, allowing users from Tenant A to sign in and use services in Tenant B.

  2. Configure Access for Target Tenant:

    • Users: Allow or block users in the target tenant to access specific resources or applications.
    • Applications: Configure which applications should be accessible to external users.
    • Collaboration settings: Configure the permissions that external users will have when interacting with your tenant.

  3. Establish Communication Between Tenants:

    • Once policies are configured, communicate with the administrators of the target tenant to verify the settings are working correctly.

Step 5: Set Up Azure AD B2B (Business to Business) Collaboration (Optional)

If you want to allow users from the source tenant to access resources like applications, documents, and other resources in the target tenant, you can use Azure AD B2B (Business-to-Business) collaboration.

  • Configure B2B settings in the source tenant:
    • Enable external collaboration settings that allow users to invite external accounts from another tenant.
    • This includes specifying whether external accounts can invite other users or share resources.
  • Invite Users for Access:
    • After configuring the settings, you can start inviting users from the source tenant to access the target tenant’s resources via B2B collaboration.

Step 6: User Synchronization (Optional for On-Premises Integration)

If you're using Azure AD Connect to synchronize on-premises Active Directory with Azure AD, you can synchronize the users from your on-premises AD to the source Azure AD tenant.

  1. Install and Configure Azure AD Connect on your on-premises server.
  2. Select the appropriate synchronization options for user identity management (password hash synchronization, federated authentication, etc.).
  3. Enable Cross-Tenant Synchronization once the on-premises AD is synced to the Azure AD tenant. This will ensure that users who are synced from the on-premises Active Directory to the source Azure AD tenant will also be part of the cross-tenant access configuration.

Step 7: Test the Setup

  1. Test Cross-Tenant Access:

    • After setting up cross-tenant synchronization, test by trying to access resources in the target tenant using a user from the source tenant.
    • Verify the synchronization and access policies work as intended.

  2. Check Logging and Monitoring:

    • Check the Azure AD logs for any authentication issues, access denials, or synchronization problems.
    • Monitor the success or failure of access requests between tenants using Azure AD Sign-In logs and Audit Logs.

Step 8: Fine-Tuning and Troubleshooting

  1. Review and Adjust Access Permissions:

    • As you test the synchronization, fine-tune user access policies and collaboration settings to ensure external users are able to use only the intended resources.

  2. Resolve Synchronization Issues:

    • If there are any problems, check the Azure AD Connect logs and Cross-Tenant Access logs for detailed error messages.
    • Ensure that both source and target tenants have been correctly configured and that there are no conflicting access policies.

  3. Use Azure AD Security Center:

    • If you encounter security-related issues, Azure AD Security Center can be used to monitor for potential risks and vulnerabilities in cross-tenant access configurations.

Summary of Cross-Tenant Synchronization Workflow

  1. Source Tenant: Configure Azure AD Cross-Tenant Access Settings.
  2. Target Tenant: Configure Azure AD Cross-Tenant Access Settings.
  3. Policy Creation: Define cross-tenant access policies and permissions.
  4. Optional B2B: Set up Azure AD B2B collaboration for external users.
  5. Synchronization (Optional): If syncing on-prem AD, use Azure AD Connect to synchronize identities.
  6. Test: Test cross-tenant synchronization and troubleshoot as needed.
  7. Monitor: Use Azure AD monitoring tools to ensure smooth operation.

By completing these steps, you can configure cross-tenant synchronization between two or more Azure AD tenants, allowing users to collaborate seamlessly while maintaining secure access control.

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