Microsoft Entra ID B2B Collaboration Architecture

The Sovereign Bridge of Partnership

B2B (Business-to-Business) Collaboration is the “Sovereign Bridge” that connects your Microsoft Entra ID tenant to the outside world. It allows you to securely share your applications and resources with guest users from other organizations while maintaining complete control over your own data. In the modern interconnected enterprise, identity is no longer confined to your payroll; it extends to vendors, partners, and consultants. For the IAM architect, B2B is the framework for Federated Trust, ensuring that external identities are governed with the same rigor as internal users, without the overhead of managing their credentials.

Core Mission

Secure Boundary Navigation. Enabling seamless resource sharing with external partners while enforcing universal security policies and automating the guest user lifecycle.

Like a Guest Visitor Pass: Imagine your office building (The Tenant). A partner (Guest User) arrives. You don't give them a permanent employee badge or put them on the payroll. Instead, they use their own State ID (Their Home IdP) to prove who they are. You issue them a temporary "Visitor Pass" (The Guest Object) that only opens the doors to the specifically authorized conference rooms (The Shared Apps). When they leave your project, you simply deactivate the pass.

Vendor Collaboration / Supply Chain Access / External Consulting / Joint Ventures

The External Identity Matrix

Managing B2B requires balancing ease-of-onboarding with rigid security guardrails.

Strategic Collaboration Profiles

Profile	Strategic Responsibility	IAM Implementation
Cross-Tenant Sync	Seamless Multi-Tenant Org.	Automatic user provisioning between trusted Entra ID tenants.
B2B Collaboration	Standard Guest Access.	Redemption-based invitation (Email/SAML/Google).
External Identities	Customer & Partner CIAM.	Self-service sign-up / API-driven onboarding.
B2B Direct Connect	Teams Shared Channels.	No guest object required; seamless resource access within the app.

The Partner Onboarding Flow

B2B collaboration follows a “Bring Your Own Identity” (BYOI) journey, shifting credential risk back to the partner.

graph LR
    Invite[Invite Partner] --> Federalize[Federate Trust]
    Federalize --> Governance[Apply Policies]
    Governance --> Review[Periodic Audit]

Invitation & Federation

An internal user or admin invites an external partner via email. The system establishes a "Bridge of Trust" with the partner's home identity provider (Entra ID, Google, or SAML). The partner authenticates at home—you never touch their password.

Sovereign Policy Enforcement

The moment the partner enters your tenant, your **Conditional Access** policies take over. You can mandate that they use MFA (even if their home tenant doesn't require it) and restrict their access to specific applications and data sensitivity labels.

Governance & Clean-up

Guest users shouldn't live forever. Use **Access Reviews** to force business owners to periodically justify why each guest still has access. If the project ends or the review is ignored, the system automatically revokes the "Visitor Pass," closing the bridge.

Technical B2B Implementation

Controlling cross-tenant settings is critical for preventing unauthorized data exfiltration.

B2B Policy Strategy (JSON API)

// Enforcing Restricted Cross-Tenant Access
{
  "b2bCollaborationInbound": {
    "usersAndGroups": { "accessType": "allowed", "targets": ["tenant-id-here"] },
    "applications": { "accessType": "allowed", "targets": ["app-id-here"] }
  },
  "b2bCollaborationOutbound": {
    "usersAndGroups": { "accessType": "blocked" },
    "applications": { "accessType": "blocked" }
  }
}

Partnership Implementation Guides

Master the technical ceremonies of external identity and cross-tenant orchestration.

Next Steps

Explore Entra External ID for next-gen customer and partner identity.
Review Trust Settings for managing cross-tenant incoming MFA trust.
Check Microsoft Teams Shared Channels for B2B Direct Connect patterns.