What Is Microsoft Teams Direct Routing and How Does It Work?
Microsoft Teams Direct Routing connects Teams Phone to external calling through a certified SBC and chosen PSTN provider.
Choose operational ownership and test the caller journey
Review the Teams external-calling infrastructure requirements to clarify tenant and provider responsibilities. Before moving your main numbers, use the Teams number-migration guide to verify normal calls, closed hours and exception handling.
Microsoft Teams Direct Routing is a method of connecting Teams Phone to the public telephone network through a supported Session Border Controller and a chosen telephony provider. It allows organisations to use Teams for external calls while retaining more control over carriers, numbers and routing than some bundled alternatives.
The main components
- A Microsoft 365 tenant with Teams and Teams Phone licensing for relevant users.
- A Microsoft-certified Session Border Controller, or a managed provider service built on one.
- PSTN trunks and business telephone numbers.
- DNS, certificates, firewall rules and internet connectivity.
- Voice routes, dial plans and user policies in Teams.
How a call is routed
For an outbound call, Teams applies the user’s voice policy and route. Signalling passes through Microsoft’s service to the certified SBC, which connects the call to the provider’s telephone network. Media may follow the planned Microsoft and SBC path depending on configuration.
Inbound calls arrive through the provider and SBC, then Teams routes them to a user, auto attendant, call queue or other authorised destination.
Why businesses choose Direct Routing
Direct Routing can support existing carrier relationships, complex routing, analogue-device integration, international requirements or migration from another PBX. Organisations can combine it with other Microsoft PSTN connectivity options where appropriate.
Our Microsoft Teams Direct Routing service brings the SBC, PSTN connectivity, numbers and UK support into one managed design.
Licensing and tenant preparation
Microsoft’s current documentation states that Direct Routing users require Teams and Teams Phone, with additional licensing possible for some functions. Users must be correctly homed online, and the SBC FQDN must use a verified Microsoft 365 domain rather than the default onmicrosoft.com domain.
SBC and certificate requirements
Microsoft supports certified SBCs for Direct Routing. The SBC needs a public FQDN, trusted certificate and the documented signalling and media connectivity. The design should cover certificate renewal, monitoring, software support and failover.
Number management and porting
Existing business numbers may be ported to the chosen provider after validation. Direct dial, main numbers, auto attendants and queues need a documented assignment plan. Outbound presentation must use authorised, reachable numbers.
Connectivity and call quality
Users need reliable access to Microsoft 365, and the SBC and provider paths must meet signalling and media requirements. Monitor latency, jitter, packet loss and firewall changes. A working Teams chat session does not prove that voice quality will be acceptable.
Operational support boundaries
Direct Routing spans Microsoft, the SBC, telephony provider, internet service and customer tenant. Agree who investigates each layer and who coordinates faults that cross boundaries. Microsoft may require certified SBC support evidence during escalation.
Implementation sequence
- Confirm requirements, licensing and tenant domains.
- Select the certified SBC and PSTN design.
- Prepare DNS, certificates, firewall and connectivity.
- Configure routes, policies, users and test numbers.
- Test inbound, outbound, emergency and failure scenarios.
- Port numbers and monitor the live service.
Direct Routing is best treated as a managed voice architecture, not a toggle inside Teams. Talk to I.T Communications about a Teams calling design.
