Teams Direct Routing: bring your own carrier to Microsoft Teams.
Direct Routing is the door Microsoft leaves open for any carrier. It connects Microsoft Teams Phone to the public switched telephone network through a certified SBC and your carrier’s SIP trunks. SIPNEX is the carrier to bring: FCC-licensed trunks feeding your SBC — owned, integrator-run, or hosted — with A-level STIR/SHAKEN on every outbound call and carrier rates instead of per-user calling plans.
How Teams Direct Routing connects Microsoft Teams to the PSTN.
Teams is Microsoft’s unified communications platform. On its own it has no path to the phone network. Direct Routing adds one. Microsoft describes it as the way to connect your own telephony infrastructure to Microsoft Teams Phone through a supported, customer-provided Session Border Controller. Your carrier’s trunks land on that SBC. Calls then flow in both directions between Teams users and the public switched telephone network, and the same SBC can integrate third-party telephony systems you already run.
The signaling path. Your SBC talks to Microsoft over SIP/TLS on port 5061, and Microsoft forces TLS 1.2 on that interface. The SBC connects to three Microsoft FQDNs in priority order: sip.pstnhub.microsoft.com first, then sip2 and sip3 for regional failover. On the carrier side, the SBC speaks ordinary SIP to SIPNEX trunks. Translating between the two dialects is the SBC’s job.
The media path. Audio runs as SRTP. Without media bypass, it passes through Microsoft’s media processors on UDP ports 3478–3481 and 49152–53247. With media bypass, audio stays between the Teams client and the SBC. Microsoft supports SILK, G.711, G.722, and G.729 between Teams and the SBC. The carrier leg is the same SIP and RTP your existing phone system already uses.
Teams has four doors to the phone network.
Microsoft offers four PSTN connectivity options for Teams Phone. Calling Plans make Microsoft your carrier. Operator Connect uses a program-enrolled carrier that you manage from the Teams admin center. Teams Phone Mobile ties the Teams number to a mobile SIM. Direct Routing is the only one where any PSTN operator qualifies. Microsoft supports mixing all four within one tenant.
| CAPABILITY | DIRECT ROUTING | CALLING PLANS / OPERATOR CONNECT |
|---|---|---|
| Carrier choice | Any PSTN carrier | Microsoft, or program-enrolled operators only |
| Per-minute economics | Carrier rates you negotiate | Per-user plans / operator bundles |
| Local survivability (SBA) | Supported | Not available |
| Analog devices & legacy PBX interop | Via ATAs behind the SBC | Not the designed path |
| Infrastructure | Certified SBC (yours, an integrator’s, or DRaaS) | None customer-managed |
| Attestation control | Your carrier’s — SIPNEX signs A-level | Whatever the plan provides |
What a Direct Routing deployment needs.
1. Teams Phone licensing. Each user needs Teams Phone — the Teams Phone Standard add-on on Business/E3-class plans, or included with Microsoft 365 E5. With Direct Routing, Microsoft requires no additional calling license. PSTN costs move to your carrier, which is the point.
2. A certified SBC. Microsoft certifies border controllers, not carriers. AudioCodes, Ribbon, Oracle, and Cisco CUBE anchor the certified list; TE-SYSTEMS anynode, Avaya, and Nokia are on it too. Own one, let your integrator run one, or consume Direct-Routing-as-a-Service — Microsoft sanctions all three models. It supports Direct Routing only with certified SBCs on certified firmware.
3. Carrier trunks. The piece SIPNEX supplies: SIP trunks with unlimited concurrent channels, DIDs and toll-free numbers from carrier inventory, number porting handled, and every outbound call signed at A-level under our own STIR/SHAKEN certificate. It is the bring-your-own-carrier model, applied to Teams.
Connect an existing PBX and telephony infrastructure to Microsoft Teams Phone.
Direct Routing is not only for greenfield tenants. Microsoft lists integration with third-party PBXs and analog devices as a core reason to choose it. The certified SBC sits between Teams, your existing PBX, and the carrier trunk. Teams users and extensions still on the old PBX reach each other through the SBC, and both sides can share the same carrier trunks.
Analog devices stay. Elevator phones, door boxes, overhead paging, and fax lines connect through analog telephone adapters behind the SBC. Microsoft publishes a verified-interoperability list for analog devices — AudioCodes ATAs, the Cisco ATA 191, and Ribbon EdgeMarc gateways are on it. Operator Connect and Calling Plans are not designed for this path — there is no SBC to hang the ATAs on.
A phased migration. Microsoft’s own example pattern runs Calling Plan or Operator Connect for everyday PSTN calling and Direct Routing for third-party PBXs, analog devices, and specialized routing. So you can move users to Teams in waves. Your existing phone numbers port to the carrier once, and the SBC routes each number to Teams or to the old PBX. Nothing forces a flag day.
Teams Direct Routing setup, step by step.
Microsoft’s planning guide breaks a Direct Routing deployment into six steps. Each step is explained below in practical terms, with the carrier’s part marked.
- Confirm licensing and infrastructure. Every user needs Teams and Teams Phone and must be homed online in Microsoft 365. Direct Routing is not supported in Islands mode; users need Teams Only mode so calls land in the Teams client.
- Pick a certified SBC. Choose from Microsoft’s certified list and decide who runs it: you, an integrator, or a DRaaS provider. Microsoft recommends setting a maximum call limit on the SBC, taken from the SBC’s own documentation, so it alerts at capacity. Size that limit to the trunk capacity you order.
- Prepare DNS, certificate, and firewall. The SBC needs a public FQDN on a domain verified in your Microsoft 365 tenant — never *.onmicrosoft.com — and a certificate from a CA in the Microsoft Trusted Root Program. Open SIP/TLS to 5061 and the media ranges toward Microsoft’s 52.112.0.0/14 and 52.120.0.0/14 blocks.
- Pair the SBC with Teams. Use the Teams admin center under Voice → Direct Routing, or New-CsOnlinePSTNGateway in PowerShell. Pairing is proven when SIP OPTIONS get a 200 OK in both directions.
- Configure voice routing. Create PSTN usages, voice routes (a number pattern plus the SBCs that serve it), and a voice routing policy, then assign the policy to users. Give each user a Direct Routing number with Set-CsPhoneNumberAssignment; Microsoft recommends full E.164 format.
- Validate, then expand. Test inbound and outbound calls, emergency calling if configured, and failover between Microsoft’s SIP connection points. Then roll out in waves.
SIPNEX’s part sits under steps 2 through 5: trunk credentials the SBC points at, DIDs and toll-free numbers, porting your existing numbers, and A-level signing on the outbound leg. The SBC and the Teams tenant stay under your control.
Survivability, media bypass, and emergency calling.
Survivable Branch Appliance. Only Direct Routing offers local survivability. The SBA is Microsoft code that SBC vendors embed in their firmware or run as a separate appliance. When a site loses its internet link, Teams desktop clients on Windows and macOS, and Teams Phones, switch to the SBA automatically. Users keep making and receiving PSTN calls through the local SBC, with hold, resume, blind transfer, and call forwarding still working. Media bypass must be configured for it to work.
Media bypass. Media bypass keeps audio between the Teams client and the SBC instead of looping it through a Microsoft datacenter. Microsoft recommends it when users sit on the same network as the SBC. It uses ICE on the client and ICE Lite on the SBC. You switch it on per SBC with the MediaBypass setting on the online PSTN gateway.
Emergency calling. Dynamic emergency calling works with Direct Routing, but it needs more setup than the Microsoft-managed options. The SBC must be flagged as supporting PIDF/LO so location data rides in the emergency INVITE. Then you either connect an Emergency Routing Service provider — Microsoft certifies Bandwidth, Intrado, and Inteliquent — or configure the SBC for ELIN. An emergency call routing policy, which applies only to Direct Routing, defines the emergency numbers and their PSTN route.
Where Direct Routing fits in a mixed Teams tenant.
Microsoft’s planning guide gives an example of one tenant using every connectivity option at once. The pattern is instructive: the requirement-heavy workloads land on Direct Routing.
| USER TYPE | PSTN CONNECTIVITY | WHAT DRIVES THE CHOICE |
|---|---|---|
| Knowledge workers | Operator Connect | Standard office calling, managed in the Teams admin center |
| Frontline and mobile workers | Teams Phone Mobile | One number on the mobile SIM and in Teams |
| Contact centers | Direct Routing | Advanced voice routing and carrier choice |
| Analog devices and legacy PBXs | Direct Routing | ATAs and PBX interop behind the SBC |
| Small satellite offices | Microsoft Calling Plan | Simplest deployment, Microsoft as the carrier |
The contact-center row is the one that matters most for a carrier like SIPNEX. Campaign traffic does not belong on Teams seats; it belongs on dialer-grade trunks. A Direct Routing carrier that also runs dialer trunks gives you one carrier for both, with the same A-level signing on both.
How to choose a Direct Routing carrier or partner.
The SBC decides whether calls flow. The carrier decides what they cost and how they’re trusted. Four questions sort any candidate.
First, what are the per-minute rates at your actual volume — and are they published? Second, who signs your outbound calls, and at what attestation level? Third, how fast do numbers provision, and does porting run in parallel with your rollout? Fourth, when a call sounds wrong, can support read the SIP trace — or only open a ticket with someone who can?
Direct Routing exists so those answers can come from a carrier you chose on merit, not from whichever operator a program enrolled. SIPNEX puts its carrier rates on the pricing page, signs at A-level under its own STIR/SHAKEN certificate, and is registered in the FCC’s Robocall Mitigation Database.
About Teams Direct Routing with SIPNEX.
What is Direct Routing in Microsoft Teams?
Does my SIP carrier need to be certified by Microsoft?
What do I need to run Direct Routing?
Do I have to own an SBC?
Which SBC vendors are certified for Teams Direct Routing?
What’s the difference between Direct Routing and Operator Connect?
Can Teams Direct Routing connect an existing PBX and analog devices?
What ports and FQDNs does Direct Routing use between the SBC and Microsoft?
How does emergency calling work with Teams Direct Routing?
Do we keep our phone numbers when moving to Teams Direct Routing?
Why does the carrier behind Teams matter?
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