Microsoft Teams Direct Routing: The Complete Guide

Direct Routing is how you connect Microsoft Teams to your own telephony provider instead of buying calling plans directly from Microsoft. It’s the option most enterprises end up on once they outgrow “just buy numbers from Microsoft,” mainly because it keeps you in control of your carrier relationship, your rates, and your existing on-prem telephony investment.

This page is the hub for everything I’ve written about it. For the bigger picture of Teams Phone as a whole, including how Direct Routing compares to Calling Plans and Operator Connect, see my Microsoft Teams Phone: The Complete Guide.

How Direct Routing works

Direct Routing connects Teams to the PSTN through a certified Session Border Controller (SBC), a piece of hardware or software that sits between Teams and your telephony provider (or your existing PBX) and translates the call signaling between them. Microsoft doesn’t touch your carrier contract at all, it just needs the SBC to be certified and correctly configured to trust Teams as a calling endpoint.

In practice, that means three things need to be in place: a certified SBC, a SIP trunk from your telephony provider, and correct routing configuration in the Teams Admin Center so calls know where to go.

Why choose Direct Routing over Calling Plans

Calling Plans are simpler, Microsoft is your carrier, no SBC required. But Direct Routing is worth the extra setup when:

• You already have negotiated rates or contracts with a telephony provider you don’t want to abandon.
• You need a country or region Microsoft Calling Plans doesn’t cover.
• You’re integrating with an existing on-prem PBX during a phased migration to Teams.
• You need routing flexibility Microsoft’s own calling plans don’t offer, such as specific failover or least-cost routing logic.

If none of that applies to you, Calling Plans or Operator Connect will get you there with far less operational overhead. Direct Routing is the flexible option, not the default one.

SBC and network requirements

Your SBC needs to be on Microsoft’s certified list, and your firewall rules need to allow the correct Microsoft Teams IP ranges through. This is the part people get wrong most often, an SBC that isn’t configured against the current IP ranges will fail intermittently rather than obviously, which makes it a pain to troubleshoot.

I keep the current ranges documented here: Microsoft Teams Direct Routing IP addresses. For the full setup walkthrough, including SBC configuration and trunk setup, see my complete guide to Microsoft Teams Direct Routing.

Managing numbers day to day

Once Direct Routing is live, ongoing admin work happens mostly in the Teams Admin Center: assigning numbers to users, managing emergency calling locations, and troubleshooting routing issues when a number stops working correctly.

I’ve written a dedicated walkthrough for this: Manage Direct Routing numbers in the Teams Admin Center.

Frequently asked questions

Do I need a physical SBC, or can it be virtual? Either works, as long as it’s on Microsoft’s certified SBC list. Virtual SBCs running in Azure or another cloud are common for organizations that don’t want to manage physical appliances.

Can I run Direct Routing alongside Calling Plans in the same tenant? Yes. You choose the connectivity method per user, so it’s common to have some users on Direct Routing and others on Calling Plans, for example during a phased migration.

What happens if my SBC goes down? Users on that SBC lose PSTN calling until it’s restored or failover to a secondary SBC kicks in, if you’ve configured one. This is why redundant SBC pairs are standard practice for anything beyond a small deployment.

Is Direct Routing more expensive than Calling Plans? Not inherently, it depends entirely on your existing carrier rates. At scale, Direct Routing is often cheaper because you keep negotiated rates instead of paying Microsoft’s per-minute pricing, but it comes with the added cost of SBC licensing and management.

Related reading

• Microsoft Teams Phone: The Complete Guide
• Manage Direct Routing numbers in the Teams Admin Center
• What’s New in Teams Calling, Meetings and Devices

Running into a specific Direct Routing issue? Drop a comment below or find me on LinkedIn.