Voice LabTeams Phone

06 · Routing and dial plans

Islands mode and other hard stops

Some failures are not routing tweaks. They are unsupported states.

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Learn it in 5 minutes

Direct Routing is not supported in Islands mode. An SBC FQDN on onmicrosoft.com is not supported. A private CA is not a production certificate. AMR-WB is not a bypass codec. Media cannot be re-targeted mid-call.

Memorize the hard stops. They save you from debugging a dial plan that was never going to run.

Islands mode, onmicrosoft.com SBC names, private CAs, and AMR-WB with bypass are hard stops.

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Visual

Media bypass beside the signaling pathTeams clientMedia processorCertified SBCVPN or bypass off. Media hairpins through the processor.Signaling does not bypass
Two paths for Islands mode and other hard stops. RTP may skip the processor. SIP does not.
Hard stopsIslands · Unsupportedonmicrosoft.com · UnsupportedPrivate CA · Not productionAMR-WB plus bypass · Not supported
Each one is enough to stop the design. Counts in this drawing are teaching order, not customers.

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Worked example

I list the hard stops before I tune a regex.

  1. Mode Not Islands
  2. Name Verified domain
  3. Cert Public CA
  4. Codec Legal for the path

If it fails: Hours go into a route while the user is still in Islands mode.

Checklist HTML

Quiz

A colleague reports: The CRM stores 0207… and the SBC stores +44207… and they never join. Where do you start?

Which description of Caller ID policy is accurate?

A colleague reports: Customers return a call and reach an employee’s personal desk. Where do you start?

Flashcards

Ecosystem

Glossary

  • Normalization The dial plan rewrites what a person dialed into a number the routes can match, usually E.164. The first matching rule wins. Config: Put the specific rules above the general ones. Fault: A catch-all rule is first, so the emergency rule never runs.
  • Tenant dial plan A set of normalization rules you assign to users. A user can have a more specific plan than the tenant default. Config: Grant the plan to the user and test from that user. Fault: You edit the global plan and a branch with its own plan does not change.
  • PSTN usage A name that links a voice routing policy to one or more voice routes. The policy’s ordered list of usages is the permission to place those calls. Config: Create the usage, attach routes, then put the usage on the policy in the right order. Fault: International works because the international usage was left on a branch policy.
  • Voice route A number pattern plus an ordered list of SBC gateways. It does nothing until a PSTN usage on the user’s policy points at it. Config: Anchor the pattern. Test with the normalized number, not the raw digits. Fault: The route expects 10 digits and the dial plan already added +1.

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

Hours go into a route while the user is still in Islands mode.

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.

  • Plan Direct Routing — Microsoft Learn — last checked 2026-10.
  • RFC 3966 — RFC — last checked 2026-10.
  • E.164 — Wikipedia — last checked 2026-10. Wikipedia fallback for background. Confirm the vendor page before you change a tenant
  • Microsoft Teams blog index — Community — last checked 2026-10. Community index for the Microsoft Teams blog. This is the index, not a claim that a post discusses this room

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