Voice LabTeams Phone

05 · PSTN connectivity

Mixing them in one tenant

The plan page’s own example puts knowledge workers on Operator Connect, frontline on Teams Phone Mobile, contact centers on Direct Routing, and a small office on Calling Plans.

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Learn it in 5 minutes

Write a table: population, connectivity, policy, who operates the trunk. A contact center on Direct Routing and a headquarters on Operator Connect is a normal tenant, not a compromise.

The failure mode is a single voice routing policy granted to everyone. Mobile users then hairpin through an SBC they should never touch, or Calling Plan emergency calls leave the country.

Mix connectivity options with a written table and a separate voice policy for each population.

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Visual

Survivable branch timelineBranch clientsSBA and SBCMicrosoft 365WAN down. Local PSTN only.Meetings and presence are not the survivable set.
What remains when the path to Microsoft 365 drops. Lesson: Mixing them in one tenant.
Example from the plan pageKnowledge · Operator ConnectFrontline · Phone MobileContact center · Direct RoutingSmall site · Calling Plan
The plan page’s example populations. Not your org chart. Counts in this drawing are teaching order, not customers.

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Worked example

I mix options on purpose, with a policy per population.

  1. Table Population to option
  2. Policy One per population
  3. Test Each row
  4. Exception Named, not implied

If it fails: One global policy sends every population through one SBC.

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Quiz

A colleague reports: Audio dies when a transfer tries to move the RTP peer. Where do you start?

Which description of Two media ports per call is accurate?

A colleague reports: The 51st call connects with no audio. Where do you start?

Flashcards

Ecosystem

Glossary

  • Operator Connect A certified carrier manages PSTN for you inside the tenant. You need Teams Phone. You do not need a Microsoft Calling Plan or your own SBC. Config: Enable the operator in the admin center and assign the numbers they provide. Fault: Someone also builds a Direct Routing SBC for the same numbers and the routes fight.
  • Operator Connect for India The India-specific operator model. It exists because India PSTN rules are not the same as a generic Operator Connect deployment. Config: Use the current India plan article and the licensed operator there. Fault: A UK SBC was proposed as the egress for an India office.
  • Teams Phone Mobile The user’s mobile SIM number is also their Teams number, through a certified mobile operator. Teams Phone is required. Config: Assign the operator number to the user. Do not also treat it as a spare Calling Plan. Fault: One human has two different caller IDs and the CRM matches neither.
  • Direct Routing You connect a certified SBC to Teams and bring your own carrier. Users need Teams and Teams Phone. They must be homed online. Islands mode is not supported. Config: Pair the FQDN, open 5061, allow media ranges, assign a voice route. Fault: The SBC is up and the user has no voice routing policy.

Sister technologies

Around the call: compliance recording, workforce management, emergency location, analytics, CRM screen pop, and an agent with a human escape. Each one has its own failure.

Config and troubleshooting

One global policy sends every population through one SBC.

Cross-platform bridges

CUCM

Cisco CUBE is one of the SBC families named in this lab’s certification lesson. A certified release can be the Direct Routing SBC between Unified CM and Teams.

The tenant still needs a verified domain on the SBC FQDN, and the user still needs Teams Phone. The studio translator does not open a live AXL session. Confirm the current certified release before you build.

Webex

Teams Phone and Webex Calling are separate clouds. This lab does not describe a feature that registers a Webex Calling user into a Teams tenant.

A number move is usually a carrier port, a certified SBC, or a meetings interop product. Confirm before relying.

UCCE

Unified CCE stays the ACD until you migrate it. Microsoft’s contact-center articles name Connect, Extend, and Unify. They do not name a UCCE connector in the notes this lab cites.

Voice into Teams is still Direct Routing or Operator Connect. The routing script stays on the contact-center product you bought. Confirm the vendor’s current model. Source: https://learn.microsoft.com/en-us/microsoftteams/teams-contact-center.

Future hooks

Copilot Studio, Azure Communication Services, and Graph are later tracks in this lab. Treat any uncited limit as confirm before relying.

BridgesEcosystem

Sources and go deeper

Opened 2026-10. A row marked confirm did not open. Wikipedia is background. The Teams blog row is the community index.

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