What Is Direct Routing for Microsoft Teams?
Direct Routing is a way of connecting Microsoft Teams to the phone network using your own SIP trunk provider, instead of buying calling minutes directly from Microsoft. It works by placing a certified device called a session border controller, or SBC, between Teams and your telecoms provider, so calls can pass securely between the two.
In practice, it means you keep control of your own carrier, your own rates, and your own routing rules, rather than being tied to Microsoft's Calling Plans.
If you're weighing this up against the alternatives, our guide to what Microsoft Teams Calling is covers Direct Routing alongside Calling Plans and Operator Connect.
How Does Direct Routing Actually Work?
When a Teams user dials an external number, the call leaves Teams and reaches the SBC first. The SBC translates the call between Microsoft's protocols and standard SIP, then passes it on to your SIP trunk provider, who connects it to the wider phone network. Incoming calls follow the same path in reverse.
The SBC does more than just pass calls through. It also handles encryption, access control, call quality monitoring, and — critically — the location information Teams needs to route 999 calls correctly.
What Do You Need to Set Up Direct Routing?
Direct Routing has more moving parts than Microsoft's own Calling Plans, which is the trade-off for the extra control it gives you. You'll typically need:
- A Teams Phone licence for every user who'll make external calls
- A Microsoft-certified SBC — either a physical appliance or, more commonly now, a cloud-hosted SBC from a certified provider such as AudioCodes or Ribbon
- A SIP trunk from a telecoms provider, either your existing one or a new contract
- A verified domain in Microsoft 365, with the correct DNS records configured
- Voice routing policies and dial plans set up in the Teams admin centre
This isn't a same-day setup. Getting the domain verification, DNS records and SBC configuration right takes proper planning, which is where a lot of DIY attempts run into trouble.
Direct Routing vs Calling Plans vs Operator Connect
| Direct Routing | Calling Plan | Operator Connect | |
|---|---|---|---|
| Who's the carrier | Your own SIP trunk provider | Microsoft | A certified telecoms partner |
| Setup complexity | Highest — requires an SBC | Lowest | Low to medium |
| Cost at scale | Usually the cheapest per minute | Usually the most expensive | Mid-range |
| Control over routing | Full control | Limited | Moderate |
| Best suited to | Businesses with existing contracts or complex routing needs | Small teams wanting the simplest option | Businesses wanting managed calling without their own SBC |
Broadly, the more calling volume and complexity a business has, the more Direct Routing tends to make financial sense — the setup cost gets absorbed by the ongoing savings on call charges.
Why Would a Business Choose Direct Routing?
The most common reason is keeping an existing telecoms contract rather than switching everything to Microsoft. Businesses that have negotiated good rates with a carrier, or that need calling in countries Microsoft's Calling Plans don't cover well, often find Direct Routing the more practical route.
It's also the option that gives you the most flexibility around call routing rules — useful if different sites, departments or countries need to handle calls differently.
What Are the Downsides?
Direct Routing needs proper technical setup and ongoing management. Someone has to own the SBC configuration, keep DNS records correct, and troubleshoot if call quality issues appear — this isn't something you switch on and forget. For smaller businesses without in-house IT resource, Calling Plans or Operator Connect are usually a more realistic starting point, even if they cost more per user.
Frequently Asked Questions
Do I need to buy my own SBC hardware? Not necessarily. Many providers now offer cloud-hosted SBCs, so you don't need to install and maintain physical hardware on-site.
Can I use any SIP trunk provider with Direct Routing? You can use any SIP trunk provider, but it has to connect through a Microsoft-certified SBC. Not every telecoms provider offers this as standard, so it's worth checking before committing.
Is Direct Routing more reliable than Calling Plans? Not inherently — reliability depends on your SBC provider and SIP trunk quality, not the method itself. Both routes can be set up to a high standard if configured properly.
Does Direct Routing support 999 calls? Yes, but the SBC needs to be configured with accurate location data for each user or site, so emergency calls are routed to the right service. This is a compliance requirement, not an optional extra.
Direct Routing can save money at scale, but it's easy to get wrong without the right setup. Request a quote for independent advice on whether it's the right fit for your business, or compare it against other systems with our phone system finder.
