# Unified CM and Teams Phone coexistence during a migration

Canonical: https://warmtransfer.net/knowledge/cucm-teams-coexistence

Last verified: 2026-09-25

Microsoft Direct Routing integrates Microsoft Teams Phone with existing telephony environments by using a certified Session Border Controller (SBC)[^13][^23]. In a coexistence architecture, the SBC connects Teams Phone to both an existing PBX and the PSTN carrier[^23].

## SBC Architecture and Signaling

Direct Routing requires a Microsoft-certified Session Border Controller, and Microsoft supports Teams Phone with Direct Routing only when certified SBCs are used[^13]. Direct Routing certification is granted to specific SBC firmware versions, and higher firmware is supported as long as the major.minor version remains the same[^4]. Microsoft states it is not accepting new nominations for Direct Routing SBC certification until further notice[^38].

Cisco Unified Border Element (CUBE) models appear on Microsoft's certified SBC list:
- CUBE for 4000 Series ISRs is certified for Direct Routing (both non-media-bypass and media bypass), supported from IOS XE Amsterdam 17.2.1r, with 17.6.1a recommended[^8].
- CUBE for Catalyst 8000 Edge Platforms is certified for Direct Routing, supported from IOS XE 17.3.2, with 17.6.1a recommended[^7].
- In Microsoft's certified SBC table, Cisco CUBE entries are marked 911 Service Provider Capable, but not ELIN capable[^9].

The SBC FQDN must belong to a verified domain in the Microsoft 365 tenant, and the default *.onmicrosoft.com domain cannot be used[^20]. For Microsoft 365, Office 365, and GCC environments, the SBC connects over SIP/TLS to destination port 5061 on `sip.pstnhub.microsoft.com`, `sip2.pstnhub.microsoft.com`, and `sip3.pstnhub.microsoft.com` in that priority order[^21]. Direct Routing media between Microsoft media processors and the SBC uses UDP/SRTP on ports 3478-3481 and 49152-53247 bidirectionally[^15]. Supported codecs between Teams and the SBC are SILK, G.711, G.722, G.729, and AMR-WB, with AMR-WB available for non-bypass calls only[^14]. Microsoft does not support media re-targeting during an active Direct Routing call; if the SBC signals a new media IP, Teams never sends media to it[^17].

Cisco states that if applications using a Unified CM SIP trunk experience SIP interoperability issues, a default SIP Normalization or Transparency script may be needed, and a SIP profile can carry an SDP transparency profile[^10]. For Direct Routing support issues, the customer contacts the SBC vendor first, and that vendor escalates to Microsoft if needed; Microsoft may decline cases that involve non-certified SBCs[^22]. Microsoft's "Migrate to Direct Routing" documentation covers migrations from Calling Plans, Skype for Business Server on-premises PSTN, and Cloud Connector Edition, leaving SBC configuration for the new route to the SBC vendor's documentation[^36].

## Direct Routing Call Routing

Direct Routing call routing is constructed from an online voice routing policy containing ordered PSTN usages[^53]. Each usage holds voice routes, and each route pairs a called-number pattern with a set of online PSTN gateways (SBCs)[^53]. PSTN usages in an online voice routing policy are evaluated in order; once a match is found in one usage, later usages are never evaluated[^49]. WarmTransfer's reading of the sources is that if one voice routing policy has both a specific route for Unified CM-held numbers and a broad catch-all PSTN route in separate PSTN usages, the Unified CM usage probably has to come first, or calls to Unified CM users would leave through the catch-all route[^32]. Route priorities determine which voice route is tried first, but SBCs configured inside a single voice route are tried in random order[^54]. When an incoming PSTN call is forwarded or transferred and the ingress SBC is also an eligible egress SBC, Teams ignores that SBC's priority value and tries it first[^34].

If a user has only Teams Phone without Calling Plan and the dialled number matches no route in their online voice routing policy, the call is dropped[^37]. If the called number contains an extension (such as +1425XXXXXXX;ext=YYY), the voice route number pattern is applied only to the part without the extension[^41].

Direct Routing can be combined with Calling Plan or Operator Connect within a single tenant, and Microsoft describes using Direct Routing for calls to third-party PBXs while Calling Plan or Operator Connect handles PSTN calling as a common pattern[^16]. If a Calling Plan user is assigned an online voice routing policy, calls matching a policy pattern exit via Direct Routing, while non-matching calls use Calling Plan infrastructure[^3]. Every voice-enabled user inherits the global (org-wide default) online voice routing policy, which can send Calling Plan and Operator Connect users' PSTN calls to a Direct Routing trunk by accident; Microsoft recommends custom policies assigned per user instead[^28].

## Dial Plans and Number Translation

Microsoft states that the usual reason for a custom Teams dial plan is to support non-E.164 dialling such as extensions or abbreviated national dialling, and that Direct Routing or extension dialling requires extra call-routing configuration[^11]. When normalising a dialled number, Teams gives user dial plan rules precedence over the tenant (Global) dial plan, and tenant rules precedence over the Microsoft-managed service dial plan; a user cannot hold a tenant and a user dial plan at the same time[^12]. A tenant can have at most 1,000 tenant dial plans[^35].

Direct Routing number translation rules are attached per SBC via `New-CsOnlinePSTNGateway` or `Set-CsOnlinePSTNGateway` using the `InboundTeamsNumberTranslationRules`, `InboundPSTNNumberTranslationRules`, `OutboundTeamsNumberTranslationRules`, and `OutboundPSTNNumberTranslationRules` parameters, applying in that exact order[^57]. A tenant can have at most 400 translation rules in total, where a pattern can be at most 1024 symbols and a translation at most 256[^56]. Microsoft's example demonstrates an inbound translation rule on the SBC profile (pattern `^(\d{4})$` translating to `+1206555$1`) that expands a 4-digit called number arriving from the SBC into the E.164 number assigned to the Teams user[^29]. To avoid double normalisation, Microsoft recommends that Direct Routing customers normalise numbers to include a "+" in dial plans and then remove the "+" with a route-based translation rule if the SBC requires it[^39].

WarmTransfer's reading of the sources is that to maintain extension dialling across Unified CM and Teams during a wave migration, the Teams side probably needs a dial plan rule that expands short extensions to E.164 and a voice route whose pattern covers numbers still on Unified CM pointing to the SBC, while Unified CM requires mirror routing toward the SBC for numbers that have moved[^30].

Teams routes inbound calls by Reverse Number Lookup (RNL) on the called number; if the called number does not match an assigned user or resource account number exactly, the call fails or follows unassigned number routing if configured[^51]. For Direct Routing, a user's number can be 3 to 38 digits without common symbols, whereas Calling Plan and Operator Connect numbers are E.164[^19]. A Teams number can carry an extension of 1 to 12 digits after the `;ext=` delimiter; if assigned, the inbound called number must include it for RNL to match, and Microsoft notes that extensions are only needed when users share a main number without a Shared Calling policy[^52].

Teams unassigned number routing can direct calls for unassigned numbers, either individually or as a regex range, to a user, a resource account for an auto attendant or call queue, or an announcement; Microsoft advises range rules over thousands of single-number rules[^60]. Unassigned number treatment checks the called number on both inbound calls to Teams and outbound calls from Teams, causing outbound calls to external numbers inside a configured range to follow the treatment[^59]. WarmTransfer's reading of the sources is that an unassigned number treatment whose range includes numbers still homed on Unified CM would probably catch outbound Teams calls to those users and apply the treatment instead of sending them to the SBC, so ranges should probably exclude numbers still on Unified CM[^31].

## User Provisioning, Modes, and Forwarding

Direct Routing users must be homed online in Microsoft 365 and require Microsoft Teams and Teams Phone licences[^25]. Direct Routing requires users to be in Teams Only mode to ensure incoming calls land in the Microsoft Teams client[^55]. Teams "coexistence modes" (Islands, Skype for Business only, the 2 Skype for Business with Teams modes, and Teams only) describe coexistence between Skype for Business and Teams, not with a third-party PBX; modes other than Teams Only can be applied only to users homed in Skype for Business Server on-premises[^6]. Direct Routing is not supported in Islands mode[^18].

An online-managed Direct Routing number is assigned using `Set-CsPhoneNumberAssignment -PhoneNumberType DirectRouting`, which also enables Enterprise Voice for the user[^2]. Uploading Direct Routing numbers to Microsoft's inventory is optional because assigning a number uploads it automatically, though a PowerShell upload request supports up to 10,000 numbers[^24].

Admin management of user call forwarding and delegation operates only in Teams Only mode, requires a Teams Phone licence, and uses `Get-CsUserCallingSettings` and `Set-CsUserCallingSettings` from Teams PowerShell module 4.0 or later[^27]. Forwarding and simultaneous ringing to external phone numbers depend on the calling policy setting "Call forwarding and simultaneous ringing to external phone numbers", which is enabled by default[^26].

## Voicemail

Cloud Voicemail is set up automatically for Teams users and stores messages in the user's Exchange mailbox (Exchange Online or Exchange Server); it does not support third-party email systems[^5]. With the Teams calling policy `AllowVoicemail` set to `AlwaysEnabled`, unanswered calls always route to voicemail after 30 seconds of ringing; with `AlwaysDisabled` they never do; and `UserOverride` (the default) follows the user's configured forwarding and unanswered settings[^1]. If neither the user nor an administrator modifies call answering rules, unanswered Teams calls go to voicemail after 30 seconds, even though the Teams admin center and PowerShell show the unanswered target as none with a 20-second delay[^58].

An SBC can send a Direct Routing call straight to a Teams user's voicemail without ringing the user by adding `opaque=app:voicemail` to the Request-URI[^40]. WarmTransfer's reading of the sources is that during a phased migration, a user moved to Teams receives Cloud Voicemail automatically, while users remaining on Unified CM keep their existing voicemail platform, with no source mechanism documented for migrating existing greetings or messages between the two[^33].

## Number Porting to Calling Plans

Before Direct Routing numbers are ported to another Teams PSTN option, they must be unassigned from users and released from Microsoft's number inventory with `New-CsOnlineTelephoneNumberReleaseOrder`[^50]. When porting hybrid numbers—meaning numbers moving from Direct Routing or Operator Connect to Calling Plans—Microsoft asks customers to contact the Telephone Number Services (TNS) service desk and flag them as hybrid[^44]. For numbers already used with Direct Routing or Operator Connect in the US or Canada, preassignment is not allowed during a Calling Plan port, but existing assignments can be retained if each number has a Calling Plan licence and an emergency location before the port completes; outside the US and Canada, these numbers arrive unassigned[^43].

A port request of 1,000 numbers or more must bypass the Teams admin center porting wizard and be submitted manually through the TNS service desk[^45]. Port requests against the same carrier account are processed 1 at a time; a second batch from that account must wait until the first port completes, or the losing carrier will reject overlapping requests[^48]. Microsoft advises against disconnecting service with the existing provider before porting finishes, because inactive or disconnected numbers cannot be ported[^47].

Microsoft notes that a Calling Plan port typically takes 7-14 days end to end and up to 30 days depending on the losing carrier[^46]. In the US, ports require at least 5 days of lead time, while Canada requires at least 10 days, and target dates cannot be set more than 30 calendar days out[^46]. Microsoft recommends choosing a conservative target port date at least 15 business days after submission for all ports to improve predictability[^42].

## Applicability

Applies to: Microsoft Teams Phone Direct Routing, Microsoft Teams Phone, Microsoft Teams, Microsoft Teams Phone Cloud Voicemail, Microsoft Teams Calling Plans, and Cisco Unified Communications Manager. Deployments: on-premises and multi-tenant. Sources checked 2026-09-25. CUBE platforms are certified for 4000 Series ISRs from IOS XE Amsterdam 17.2.1r (17.6.1a recommended) and Catalyst 8000 Edge Platforms from IOS XE 17.3.2 (17.6.1a recommended)[^8][^7]. Direct Routing SIP signaling endpoints apply globally to commercial Microsoft 365, Office 365, and GCC tenants, while GCC High and DoD use different FQDNs[^21]. Specific lead times and preassignment rules for porting apply to Calling Plan markets, specifically the US and Canada[^46][^43].

## What remains uncertain

The following topics and technical details are not covered by the sources below:
- Cisco application notes detailing Direct Routing for Microsoft Phone System with Unified CM via CUBE are not covered by the sources below.
- Handling emergency calling during the split, including Teams dynamic E911 versus Unified CM ELIN on a shared SBC, is not covered by the sources below.
- Configuration of Unified CM route patterns and Calling Search Spaces (CSS) toward the SBC for number ranges that have moved to Teams is not covered by the sources below.
- Operator Connect number moves and carrier-side phased porting for Direct Routing trunks are not covered by the sources below.
- Use of the Teams SIP Gateway to reuse Cisco phones during the migration is not covered by the sources below.
- Migration of Cisco Unity Connection messages and greetings into Teams Cloud Voicemail is not covered by the sources below.
- Unified CM Call Forward All to Teams via SBC, including CSS and redirecting number handling, is not covered by the sources below.
- Simultaneous ringing between Unified CM (Single Number Reach) and Teams is not covered by the sources below.

## Sources

[^1]: With the Teams calling policy AllowVoicemail set to AlwaysEnabled, unanswered calls always go to voicemail after 30 seconds of ringing; with AlwaysDisabled they never do; UserOverride (the default) follows each user's forwarding and unanswered settings. Source: [Set up Cloud Voicemail](https://learn.microsoft.com/en-us/microsoftteams/set-up-phone-system-voicemail), Control routing of calls to Cloud Voicemail > Using PowerShell. Checked 2026-09-25.
[^2]: An online-managed Direct Routing number is assigned with Set-CsPhoneNumberAssignment -PhoneNumberType DirectRouting, which also enables Enterprise Voice for the user. Source: [Enable users for Direct Routing](https://learn.microsoft.com/en-us/microsoftteams/direct-routing-enable-users), Configure the phone number and enable enterprise voice > Use PowerShell. Checked 2026-09-25.
[^3]: If a Calling Plan user is also assigned an online voice routing policy, calls matching a policy pattern go out through Direct Routing and non-matching calls use the Calling Plan infrastructure. Source: [Configure call routing for Direct Routing](https://learn.microsoft.com/en-us/microsoftteams/direct-routing-voice-routing), Voice routing policy considerations section, first paragraph. Checked 2026-09-25.
[^4]: Direct Routing certification is granted to specific SBC firmware versions; higher firmware is supported as long as the major.minor version is the same. Source: [Session Border Controllers certified for Direct Routing - Microsoft Teams](https://learn.microsoft.com/en-us/microsoftteams/direct-routing-border-controllers), Introductory note above the Certified SBC vendors table. Checked 2026-09-25.
[^5]: Cloud Voicemail is set up automatically for Teams users and stores messages in the user's Exchange mailbox (Exchange Online or Exchange Server); it does not support third-party email systems. Source: [Set up Cloud Voicemail](https://learn.microsoft.com/en-us/microsoftteams/set-up-phone-system-voicemail), Introductory paragraphs; Cloud Voicemail provisioning; Cloud Voicemail storage. Checked 2026-09-25.
[^6]: Teams 'coexistence modes' (Islands, Skype for Business only, the two Skype for Business with Teams modes, and Teams only) describe coexistence between Skype for Business and Teams, not with a third-party PBX; modes other than Teams Only can be applied only to users homed in Skype for Business Server on-premises. Source: [Set your coexistence and upgrade settings](https://learn.microsoft.com/en-us/microsoftteams/setting-your-coexistence-and-upgrade-settings), Set upgrade options for all users; Set upgrade options for a single user, step 3. Checked 2026-09-25.
[^7]: CUBE for Catalyst 8000 Edge Platforms is listed as certified for Direct Routing, supported from IOS XE 17.3.2 with 17.6.1a recommended. Source: [Session Border Controllers certified for Direct Routing - Microsoft Teams](https://learn.microsoft.com/en-us/microsoftteams/direct-routing-border-controllers), Certified SBC vendors table, Cisco row 'Catalyst 8000 Edge Platforms'. Checked 2026-09-25.
[^8]: Cisco Unified Border Element for 4000 Series ISRs is listed as certified for Direct Routing (non-media-bypass and media bypass), supported from IOS XE Amsterdam 17.2.1r with 17.6.1a recommended. Source: [Session Border Controllers certified for Direct Routing - Microsoft Teams](https://learn.microsoft.com/en-us/microsoftteams/direct-routing-border-controllers), Certified SBC vendors table, Cisco rows. Checked 2026-09-25.
[^9]: In Microsoft's certified SBC table the Cisco CUBE rows are marked 911 Service Provider Capable but not ELIN capable. Source: [Session Border Controllers certified for Direct Routing - Microsoft Teams](https://learn.microsoft.com/en-us/microsoftteams/direct-routing-border-controllers), Certified SBC vendors table, Cisco rows, columns '911 Service Provider Capable' and 'ELIN capable'. Checked 2026-09-25.
[^10]: Cisco says that if applications using a Unified CM SIP trunk have SIP interoperability issues, a default SIP Normalization or Transparency script may be needed, and a SIP profile can carry an SDP transparency profile. Source: [System Configuration Guide for Cisco Unified Communications Manager Release 15 and SUs - Configure Trunks](https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucm/admin/15/systemConfig/cucm_b_system-configuration-guide-15/cucm_b_system-configuration-guide-14_chapter_01000.html), Configure Trunks chapter, SIP profile and SIP trunk configuration tasks. Checked 2026-09-25.
[^11]: Microsoft says the usual reason for a custom Teams dial plan is to support non-E.164 dialling such as extensions or abbreviated national dialling, and that Direct Routing or extension dialling needs extra call-routing configuration. Source: [Microsoft Teams Dial plans for phone call routing](https://learn.microsoft.com/en-us/microsoftteams/what-are-dial-plans), Planning for tenant dial plans, Step 1; User dial plans with Direct Routing or extension dialing section. Checked 2026-09-25.
[^12]: When normalising a dialled number, Teams gives user dial plan rules precedence over the tenant (Global) dial plan, and tenant rules precedence over the Microsoft-managed service dial plan; a user cannot hold a tenant and a user dial plan at the same time. Source: [Microsoft Teams Dial plans for phone call routing](https://learn.microsoft.com/en-us/microsoftteams/what-are-dial-plans), Dial plan scopes and a user's effective dial plan section. Checked 2026-09-25.
[^13]: Direct Routing requires a Microsoft-certified Session Border Controller, and Microsoft supports Teams Phone with Direct Routing only when certified SBCs are used. Source: [Plan Direct Routing](https://learn.microsoft.com/en-us/microsoftteams/direct-routing-plan), Infrastructure requirements table (Session Border Controller row); Support boundaries section. Checked 2026-09-25.
[^14]: Direct Routing supports SILK, G.711, G.722, G.729 and AMR-WB between Teams and the SBC, with AMR-WB available for non-bypass calls only. Source: [Plan Direct Routing](https://learn.microsoft.com/en-us/microsoftteams/direct-routing-plan), Supported codecs section. Checked 2026-09-25.
[^15]: Direct Routing media between the Microsoft media processors and the SBC uses UDP/SRTP on ports 3478-3481 and 49152-53247 in both directions. Source: [Plan Direct Routing](https://learn.microsoft.com/en-us/microsoftteams/direct-routing-plan), Media ports table. Checked 2026-09-25.
[^16]: Direct Routing can be combined with Calling Plan or Operator Connect in one tenant, and Microsoft describes using Direct Routing for calls to third-party PBXs while Calling Plan or Operator Connect carries PSTN calling as a common pattern. Source: [Plan Direct Routing](https://learn.microsoft.com/en-us/microsoftteams/direct-routing-plan), Direct Routing with Calling Plan and Operator Connect section. Checked 2026-09-25.
[^17]: Microsoft does not support media re-targeting during an active Direct Routing call: if the SBC signals a new media IP, Teams never sends media to it. Source: [Plan Direct Routing](https://learn.microsoft.com/en-us/microsoftteams/direct-routing-plan), Supported codecs section, Note. Checked 2026-09-25.
[^18]: Direct Routing is not supported in Islands mode. Source: [Plan Direct Routing](https://learn.microsoft.com/en-us/microsoftteams/direct-routing-plan), Licensing requirements section, Note. Checked 2026-09-25.
[^19]: For Direct Routing, a user's number can be 3 to 38 digits without common symbols, whereas Calling Plan and Operator Connect numbers are E.164. Source: [Microsoft Teams Dial plans for phone call routing](https://learn.microsoft.com/en-us/microsoftteams/what-are-dial-plans), Number lookup for inbound calls section, Number bullet. Checked 2026-09-25.
[^20]: The SBC FQDN must belong to a verified domain in the Microsoft 365 tenant; the default *.onmicrosoft.com domain cannot be used. Source: [Plan Direct Routing](https://learn.microsoft.com/en-us/microsoftteams/direct-routing-plan), SBC domain names section. Checked 2026-09-25.
[^21]: For Microsoft 365, Office 365 and GCC, the SBC connects over SIP/TLS to destination port 5061 on sip.pstnhub.microsoft.com, sip2.pstnhub.microsoft.com and sip3.pstnhub.microsoft.com, in that priority order. Source: [Plan Direct Routing](https://learn.microsoft.com/en-us/microsoftteams/direct-routing-plan), SIP signaling: FQDNs table; SIP signaling ports table. Checked 2026-09-25.
[^22]: For Direct Routing issues the customer contacts the SBC vendor first, and the vendor escalates to Microsoft if needed; Microsoft may decline cases that involve non-certified SBCs. Source: [Plan Direct Routing](https://learn.microsoft.com/en-us/microsoftteams/direct-routing-plan), Support boundaries section. Checked 2026-09-25.
[^23]: Microsoft lists integration with third-party PBXs or analog devices as one of the reasons Direct Routing is a good fit, and its architecture diagram shows the certified SBC connecting Teams Phone to both an existing PSTN carrier and an existing PBX. Source: [Plan Direct Routing](https://learn.microsoft.com/en-us/microsoftteams/direct-routing-plan), Why choose Direct Routing? section; Direct Routing architecture section (text diagram). Checked 2026-09-25.
[^24]: Uploading Direct Routing numbers to Microsoft's inventory is optional, since assigning a number uploads it automatically; a PowerShell upload request supports up to 10,000 numbers. Source: [Enable users for Direct Routing](https://learn.microsoft.com/en-us/microsoftteams/direct-routing-enable-users), Upload Direct Routing numbers to your tenant section; Use PowerShell subsection. Checked 2026-09-25.
[^25]: Direct Routing users must be homed online in Microsoft 365 and need Microsoft Teams and Teams Phone licences. Source: [Plan Direct Routing](https://learn.microsoft.com/en-us/microsoftteams/direct-routing-plan), Infrastructure requirements table (User registrar row); Licensing requirements section. Checked 2026-09-25.
[^26]: Forwarding and simultaneous ringing to external phone numbers depend on the calling policy setting 'Call forwarding and simultaneous ringing to external phone numbers', which is on by default. Source: [Configure call forwarding and delegation settings](https://learn.microsoft.com/en-us/microsoftteams/user-call-settings), Use the Teams admin center, step 7 Note. Checked 2026-09-25.
[^27]: Admin management of user call forwarding and delegation works only in Teams Only mode, needs a Teams Phone licence, and uses Get- and Set-CsUserCallingSettings from Teams PowerShell module 4.0 or later. Source: [Configure call forwarding and delegation settings](https://learn.microsoft.com/en-us/microsoftteams/user-call-settings), Important note under the introduction; License required; Use PowerShell. Checked 2026-09-25.
[^28]: Every voice-enabled user inherits the global (org-wide default) online voice routing policy, which can send Calling Plan and Operator Connect users' PSTN calls to a Direct Routing trunk by accident; Microsoft recommends custom policies assigned per user instead. Source: [Configure call routing for Direct Routing](https://learn.microsoft.com/en-us/microsoftteams/direct-routing-voice-routing), Voice routing policy considerations section, Caution item 1. Checked 2026-09-25.
[^29]: Microsoft's example shows an inbound translation rule on the SBC profile (pattern ^(\d{4})$ to +1206555$1) that expands a four-digit called number arriving from the SBC into the E.164 number assigned to the Teams user. Source: [Translate phone numbers for Direct Routing](https://learn.microsoft.com/en-us/microsoftteams/direct-routing-translate-numbers), Example SBC configuration table (AddE164SeattleAreaCode); Example 2: Inbound call to a four-digit number. Checked 2026-09-25.
[^30]: To keep extension dialling across Unified CM and Teams during wave migration, the Teams side probably needs a dial plan rule that expands short extensions to E.164 and a voice route whose pattern covers the numbers still on Unified CM, pointing at the SBC; Unified CM needs the mirror routing toward the SBC for numbers that have moved (inferred). Source: [Microsoft Teams Dial plans for phone call routing](https://learn.microsoft.com/en-us/microsoftteams/what-are-dial-plans), Planning for tenant dial plans Step 1; combined with ms-learn-dr-voice-routing Call routing overview. Checked 2026-09-25.
[^31]: An unassigned number treatment whose range includes numbers still homed on Unified CM would probably also catch outbound Teams calls to those users and apply the treatment instead of sending them to the SBC, so ranges should probably exclude numbers still on Unified CM (inferred). Source: [Configure routing options for unassigned phone numbers](https://learn.microsoft.com/en-us/microsoftteams/routing-calls-to-unassigned-numbers), Notes section, last two bullets. Checked 2026-09-25.
[^32]: If one voice routing policy has both a specific route for Unified CM-held numbers and a broad catch-all PSTN route in separate PSTN usages, the Unified CM usage probably has to come first, or calls to Unified CM users would leave through the catch-all route (inferred). Source: [Configure call routing for Direct Routing](https://learn.microsoft.com/en-us/microsoftteams/direct-routing-voice-routing), Example 2 Note on PSTN usage order; Step 3 ordering bullets. Checked 2026-09-25.
[^33]: During the split, a user who has moved to Teams gets Cloud Voicemail automatically, while users still on Unified CM keep their existing voicemail; nothing read here documents moving existing messages or greetings between the two (inferred). Source: [Set up Cloud Voicemail](https://learn.microsoft.com/en-us/microsoftteams/set-up-phone-system-voicemail), Cloud Voicemail provisioning section. Checked 2026-09-25.
[^34]: When an incoming PSTN call is forwarded or transferred and the ingress SBC is also a possible egress SBC, Teams ignores that SBC's priority value and tries it first. Source: [Configure call routing for Direct Routing](https://learn.microsoft.com/en-us/microsoftteams/direct-routing-voice-routing), Example 1, Note after the three-route summary table. Checked 2026-09-25.
[^35]: A tenant can have at most 1,000 tenant dial plans. Source: [Microsoft Teams Dial plans for phone call routing](https://learn.microsoft.com/en-us/microsoftteams/what-are-dial-plans), Dial plans and routing considerations section. Checked 2026-09-25.
[^36]: Microsoft's 'Migrate to Direct Routing' article covers migration from Calling Plans, Skype for Business Server on-premises PSTN and Cloud Connector Edition, and leaves the SBC configuration needed for the new route to the SBC vendor's documentation. Source: [Migrate to Direct Routing](https://learn.microsoft.com/en-us/microsoftteams/direct-routing-migrating), Introductory paragraphs before 'User provisioning end-state'. Checked 2026-09-25.
[^37]: If a user has only Teams Phone (no Calling Plan) and the dialled number matches no route in their online voice routing policy, the call is dropped. Source: [Configure call routing for Direct Routing](https://learn.microsoft.com/en-us/microsoftteams/direct-routing-voice-routing), Example 1, paragraph after the third-route diagram. Checked 2026-09-25.
[^38]: Microsoft states it is not accepting new nominations for Direct Routing SBC certification until further notice. Source: [Session Border Controllers certified for Direct Routing - Microsoft Teams](https://learn.microsoft.com/en-us/microsoftteams/direct-routing-border-controllers), Sentence immediately before the Certified SBC vendors heading. Checked 2026-09-25.
[^39]: To avoid double normalisation, Microsoft recommends that Direct Routing customers normalise numbers to include a '+' in dial plans and then remove the '+' with a route-based translation rule if the SBC needs it. Source: [Translate phone numbers for Direct Routing](https://learn.microsoft.com/en-us/microsoftteams/direct-routing-translate-numbers), Route-based number translations - for outbound calls, Note. Checked 2026-09-25.
[^40]: An SBC can send a Direct Routing call straight to a Teams user's voicemail, without notifying the user, by adding opaque=app:voicemail to the Request-URI. Source: [Enable users for Direct Routing](https://learn.microsoft.com/en-us/microsoftteams/direct-routing-enable-users), Configure sending calls directly to voicemail section. Checked 2026-09-25.
[^41]: If the called number contains an extension (for example +1425XXXXXXX;ext=YYY), the voice route number pattern is applied only to the part without the extension. Source: [Configure call routing for Direct Routing](https://learn.microsoft.com/en-us/microsoftteams/direct-routing-voice-routing), Voice routing policy considerations section, Caution item 2. Checked 2026-09-25.
[^42]: Microsoft recommends a conservative target port date at least 15 business days after submission for all ports, trading speed for predictability. Source: [What's a port order? - Microsoft Teams](https://learn.microsoft.com/en-us/microsoftteams/phone-number-calling-plans/port-order-overview), Plan for port event date > Approach 2: Choosing a conservative target date. Checked 2026-09-25.
[^43]: For numbers already used with Direct Routing or Operator Connect in the US or Canada, preassignment is not allowed during a Calling Plan port, but the existing assignment can be kept if each number has a Calling Plan licence and an emergency location before the port completes; outside the US and Canada such numbers arrive unassigned. Source: [Transfer phone numbers to Microsoft Teams](https://learn.microsoft.com/en-us/microsoftteams/phone-number-calling-plans/transfer-phone-numbers-to-teams), What's the status of your port orders? table, row 'Approved (FOCAccepted)'. Checked 2026-09-25.
[^44]: When porting hybrid numbers, meaning numbers moving from Direct Routing or Operator Connect to Calling Plans, Microsoft asks customers to contact the TNS service desk and flag the numbers as hybrid. Source: [What's a port order? - Microsoft Teams](https://learn.microsoft.com/en-us/microsoftteams/phone-number-calling-plans/port-order-overview), Numbers eligible for porting, last 'You can transfer' bullet. Checked 2026-09-25.
[^45]: A port request of 1,000 numbers or more must bypass the Teams admin center porting wizard and be submitted manually through the Telephone Number Services service desk. Source: [What's a port order? - Microsoft Teams](https://learn.microsoft.com/en-us/microsoftteams/phone-number-calling-plans/port-order-overview), Large port requests section. Checked 2026-09-25.
[^46]: Microsoft says a Calling Plan port typically takes 7-14 days end to end and up to 30 days depending on the losing carrier; the US needs at least 5 days' lead time, Canada at least 10, and the target date cannot be more than 30 calendar days out. Source: [What's a port order? - Microsoft Teams](https://learn.microsoft.com/en-us/microsoftteams/phone-number-calling-plans/port-order-overview), Plan lead-time for port request processing section. Checked 2026-09-25.
[^47]: Microsoft advises against disconnecting service with the current provider before porting is complete, because inactive or disconnected numbers cannot be ported. Source: [What's a port order? - Microsoft Teams](https://learn.microsoft.com/en-us/microsoftteams/phone-number-calling-plans/port-order-overview), When to disconnect your existing phone lines with your current service provider section. Checked 2026-09-25.
[^48]: Port requests against the same carrier account are processed one at a time; a second batch from the same account must wait until the first port completes, or the losing carrier rejects the overlapping requests. Source: [What's a port order? - Microsoft Teams](https://learn.microsoft.com/en-us/microsoftteams/phone-number-calling-plans/port-order-overview), How port requests are processed section. Checked 2026-09-25.
[^49]: PSTN usages in an online voice routing policy are evaluated in order, and once a match is found in one usage the later usages are never evaluated. Source: [Configure call routing for Direct Routing](https://learn.microsoft.com/en-us/microsoftteams/direct-routing-voice-routing), Example 2: Voice routing with multiple PSTN usages, Note following the summary table. Checked 2026-09-25.
[^50]: Before Direct Routing numbers are ported to another Teams PSTN option, they must be unassigned from users and released from Microsoft's number inventory with New-CsOnlineTelephoneNumberReleaseOrder. Source: [Enable users for Direct Routing](https://learn.microsoft.com/en-us/microsoftteams/direct-routing-enable-users), Upload Direct Routing numbers to your tenant > Order history, Note. Checked 2026-09-25.
[^51]: Teams routes inbound calls by Reverse Number Lookup on the called number; if the called number does not exactly match a number assigned to a user or resource account, the call fails or follows unassigned number routing if that is configured. Source: [Microsoft Teams Dial plans for phone call routing](https://learn.microsoft.com/en-us/microsoftteams/what-are-dial-plans), Number lookup for inbound calls section. Checked 2026-09-25.
[^52]: A Teams number can carry an extension of 1 to 12 digits after the ';ext=' delimiter; if one is assigned, the inbound called number must include it for lookup to match, and Microsoft says extensions are only needed when users share a main number without a Shared Calling policy. Source: [Microsoft Teams Dial plans for phone call routing](https://learn.microsoft.com/en-us/microsoftteams/what-are-dial-plans), Number lookup for inbound calls section, Extension bullet and following paragraphs. Checked 2026-09-25.
[^53]: Direct Routing call routing is built from an online voice routing policy that contains ordered PSTN usages; each usage holds voice routes, and each route pairs a called-number pattern with a set of online PSTN gateways (SBCs). Source: [Configure call routing for Direct Routing](https://learn.microsoft.com/en-us/microsoftteams/direct-routing-voice-routing), Call routing overview section. Checked 2026-09-25.
[^54]: Route priorities decide which voice route is tried first, but the SBCs inside a single voice route are tried in random order. Source: [Configure call routing for Direct Routing](https://learn.microsoft.com/en-us/microsoftteams/direct-routing-voice-routing), Example 1: Voice routing with one PSTN usage, sentence after the call-flow diagram. Checked 2026-09-25.
[^55]: Direct Routing requires users to be in Teams Only mode so that incoming calls land in the Teams client. Source: [Enable users for Direct Routing](https://learn.microsoft.com/en-us/microsoftteams/direct-routing-enable-users), Assign Teams Only mode to users to ensure calls land in Microsoft Teams section. Checked 2026-09-25.
[^56]: A tenant can have at most 400 translation rules in total; a pattern can be at most 1024 symbols and a translation at most 256. Source: [Translate phone numbers for Direct Routing](https://learn.microsoft.com/en-us/microsoftteams/direct-routing-translate-numbers), Considerations section, Note. Checked 2026-09-25.
[^57]: Direct Routing number translation rules are attached per SBC through New- or Set-CsOnlinePSTNGateway using the InboundTeamsNumberTranslationRules, InboundPSTNNumberTranslationRules, OutboundTeamsNumberTranslationRules and OutboundPSTNNumberTranslationRules parameters, and they apply in the order listed. Source: [Translate phone numbers for Direct Routing](https://learn.microsoft.com/en-us/microsoftteams/direct-routing-translate-numbers), Considerations section; Configuring translation rules with PowerShell subsection. Checked 2026-09-25.
[^58]: If neither the user nor an admin changes call answering rules, unanswered Teams calls go to voicemail after 30 seconds, even though the Teams admin center and PowerShell show the unanswered target as none with a 20-second delay. Source: [Configure call forwarding and delegation settings](https://learn.microsoft.com/en-us/microsoftteams/user-call-settings), Additional notes section. Checked 2026-09-25.
[^59]: Unassigned number treatment checks the called number on both inbound calls to Teams and outbound calls from Teams, so an outbound call to an external number inside a configured range follows the treatment. Source: [Configure routing options for unassigned phone numbers](https://learn.microsoft.com/en-us/microsoftteams/routing-calls-to-unassigned-numbers), Notes section, last two bullets. Checked 2026-09-25.
[^60]: Teams unassigned number routing can send calls for unassigned numbers, one at a time or as a regex range, to a user, a resource account for an auto attendant or call queue, or an announcement; Microsoft advises range rules over thousands of single-number rules. Source: [Configure routing options for unassigned phone numbers](https://learn.microsoft.com/en-us/microsoftteams/routing-calls-to-unassigned-numbers), Introductory paragraphs; Notes section, first bullet. Checked 2026-09-25.