As identity ecosystems grow more complex, organizations are seeking ways to unify authentication across platforms. Microsoft Entra ID now supports External Authentication Methods (EAMs), allowing third-party identity providers like Okta to handle multi-factor authentication (MFA) during sign-in. This guide walks through the technical steps and considerations for configuring Okta as an EAM, combining insights from both Okta’s official documentation and CloudPartner.fi’s implementation experience.
Table of Contents
External Authentication Methods with Conditional Access
While External Authentication Methods (EAMs) and Conditional Access custom controls serve different purposes, they can be deployed in parallel to enhance security posture—if implemented carefully.
Recommended Configuration Strategy
Microsoft advises creating two distinct Conditional Access policies to avoid overlapping enforcement:
- Custom Control Policy: This policy triggers the custom control during user sign-in, typically used for scenarios requiring additional verification or redirection.
- MFA Enforcement Policy: This policy enforces Multi-Factor Authentication using the configured EAM, such as Okta.
Deployment Best Practices
To ensure a smooth user experience and avoid redundant prompts:
- Use separate test groups: Assign users to only one of the two policies at a time. This prevents users from encountering multiple authentication prompts in a single session.
- Avoid overlapping conditions: If a user is targeted by both policies simultaneously, they may be prompted twice—once by the custom control (which redirects to the EAM), and again by the EAM itself for MFA. This can lead to confusion and degraded user experience.
Security and Operational Benefits
This dual-policy approach enables a layered security model:
- The Custom Control Policy allows organizations to enforce tailored access requirements, such as redirecting users to a third-party verification service.
- The MFA Enforcement Policy ensures that users complete a second factor of authentication through a trusted EAM provider.
- Test group isolation allows IT teams to validate each policy independently, minimizing risk during rollout and simplifying troubleshooting.
Why Use Okta as an External Authentication Method?
Microsoft’s EAM framework was introduced to overcome the limitations of Conditional Access custom controls, which could not:
- Enforce MFA at sign-in
- Integrate with workflows like Self-Service Password Reset (SSPR), Privileged Identity Management (PIM), or Intune enrollment
- Validate specific MFA claims
- Support sign-in frequency or cross-tenant scenarios
With EAMs, Okta can now:
- Fulfill MFA claims directly during sign-in
- Integrate with Conditional Access policies
- Support advanced identity governance scenarios
Prerequisites
| Requirement | Description |
|---|---|
| Microsoft Entra ID | Admin access to register applications and configure authentication methods |
| Okta Admin Console | Access to configure integrations and assign applications |
| Redirect URI | Okta authorization endpoint: https://<your-org>.okta.com/oauth2/v1/authorize |
Configuration Steps
1. Register the App in Microsoft Entra ID
| Step | Action |
|---|---|
| 1.1 | Go to Microsoft Entra ID > App registrations > New registration |
| 1.2 | Choose Web as the platform |
| 1.3 | Set the redirect URI to Okta’s authorization endpoint |
| 1.4 | Save the Application (client) ID and Tenant ID |
2. Configure the App in Okta
| Step | Action |
|---|---|
| 2.1 | In Okta Admin Console, go to Applications > Browse App Catalog |
| 2.2 | Search for Microsoft Entra ID External Authentication Method |
| 2.3 | Enter the Tenant ID and Application ID from Entra |
| 2.4 | Choose the appropriate Tenant Type (Global, Gov, China) |
| 2.5 | Assign the app to users/groups |
| 2.6 | Copy the Client ID from the Sign On tab |
3. Create the External Authentication Method in Entra
| Step | Action |
|---|---|
| 3.1 | Go to Microsoft Entra ID > External Identities > Authentication Methods |
| 3.2 | Add a new method using the Client ID from Okta |
| 3.3 | Assign the method to a Conditional Access policy |
| 3.4 | Test the integration with a user sign-in flow |
Testing and Validation
After configuration:
- Attempt a sign-in to a Microsoft 365 app
- Ensure the Conditional Access policy triggers Okta MFA
- Verify that the sign-in logs show Okta as the authentication provider
Pro Tips from the Field
- Use test tenants to validate the flow before production rollout
- Monitor sign-in logs in both Entra and Okta for troubleshooting
- Ensure time synchronization between systems to avoid token validation errors
- Document fallback options in case of integration failure
Final Thoughts
Integrating Okta as an External Authentication Method for Microsoft Entra ID is a forward-looking strategy for organizations aiming to modernize their identity infrastructure. It not only bridges the gap between two powerful identity platforms but also unlocks advanced security and governance capabilities that were previously limited by custom controls. By following a structured configuration process and validating each step, IT teams can ensure a seamless and secure user experience across Microsoft and Okta ecosystems.
If you want to read more on EAM, see my previous blog on it
And here for Okta’s own article
