00 · Header
T2 · Webex Calling
Calling Architecture Overview
In the Unified CM migration guide, Webex Calling means the multi-tenant cloud call service. Endpoints register to that cloud. A local gateway is the bridge for PSTN and for calls between Unified CM-registered phones and cloud-registered phones. Cisco Calling Plan and Cloud Connect need no on-premises PSTN equipment. Control Hub is the portal at admin.webex.com.
01 · Executive summary
Five lines, then why it matters
- Before the move, phones and Jabber register to Unified CM. Expressway-C and Expressway-E pairs serve MRA and business-to-business. CMS, CMM, and TMS are optional. Unity Connection is optional. [cite:1]
- After the move, Webex Calling is the cloud call service. Endpoint registration and call routing live there. Webex App on Windows, Mac, Android, and iOS registers directly to Webex Calling. [cite:1]
- Control Hub assigns a local gateway to a location and then supplies the parameters you configure on CUBE. Those steps register the gateway with the cloud. PSTN for users in that location then comes through the gateway. re-check [cite:2]
- A trunk terminates on a local gateway or another supported device. A route group holds trunks for distribution or redundancy. Dial plans are global for all users. Pattern language stays in T2-R03. [cite:3]
- The migration section lists collecting location details: emergency response address, number of users, internet access, and PSTN access. Help paths named in the guide are Webex migration tools in Control Hub, certified migration providers, and Webex Setup Assist. [cite:1]
02 · Architecture map
Cloud registration, premises bridge
- 1Control Hub
- 2Calling platform
- 3Endpoints
- 4Local gateway
- 5Cloud PSTN
- 6Survivability
Mermaid source (not rendered)
flowchart LR Hub[Control Hub] --> Cloud[Webex Calling] App[Webex App] --> Cloud Cloud --> LGW[Local Gateway] LGW --> PSTN LGW --> CUCM[Unified CM]
Studio asset still required: assets/diagrams/T2-R01/arch.svg
03 · Concept deep-dive
The pieces the guide actually lists
The introduction to migrating Unified CM to Webex Calling is dated January 14, 2026. It points at the Cisco Preferred Architecture for Webex Calling for the fuller design. This room quotes the guide’s component list and the before-and-after tables. It does not invent Preferred Architecture diagrams. [cite:1]
assets/images/T2-R01/hero.png · Studio draws cloud registration beside a premises gateway.Before and after
| Side | What the guide says | Cite |
|---|---|---|
| Call control before | Unified CM. Expressway-C and Expressway-E pairs for mobile and remote access and business-to-business. | [cite:1] |
| Optional before | Cisco Meeting Server, Cisco Meeting Management, and TelePresence Management Suite. Unity Connection is optional. | [cite:1] |
| Endpoints before | Desk, Room, and Board devices, IP phones, and Jabber, registered to Unified CM. | [cite:1] |
| After | Webex Calling is the cloud call service. It handles endpoint registration and call routing. | [cite:1] |
| Directory | Directory Connector is Windows software on a domain-joined machine. Customers on Microsoft Entra ID use the Entra ID Wizard instead. | [cite:1] |
| Survivability | A Survivability Gateway is a local IOS-XE fallback during an outage. The site design is T2-R07. | [cite:1] |
PSTN choices at architecture level
| Choice | What it is | Cite |
|---|---|---|
| Local gateway | Bridge, on premises or partner-hosted. PSTN for cloud-registered endpoints, and calling between Unified CM-registered and cloud-registered endpoints. | [cite:1] |
| Cisco Calling Plan | Cloud PSTN. The migration guide says it does not require on-premises equipment. | [cite:1] |
| Cloud Connect | Cloud PSTN for Webex Calling, named alongside Cisco Calling Plan as requiring no on-premises equipment. | [cite:1] |
| Trunk | The connection from Webex Calling to the premises. It terminates on a local gateway or another supported device. | [cite:3] |
| Route group | A set of trunks used for distribution or redundancy. | [cite:3] |
| Who cloud PSTN serves | Cisco PSTN or Cloud Connected PSTN is for Webex Calling users. Calls that start on the premises do not use that cloud PSTN path. The pattern rules are T2-R03. | [cite:3] |
PPDIO, as the guide defines it
| Phase | The guide’s job for that phase | Cite |
|---|---|---|
| Prepare | Assess the current environment, gather requirements, and align stakeholders. | [cite:1] |
| Plan | Develop project plans, including timelines, resources, and risk mitigation. | [cite:1] |
| Design | Architect the target solution for the business and technical needs. | [cite:1] |
| Implement | Execute the migration according to the design, and validate function and performance. | [cite:1] |
| Optimize | Improve the solution after implementation by monitoring, refining configuration, and using automation. | [cite:1] |
| Location facts in the migration section | The section lists collecting the emergency response address, the number of users, internet access, and PSTN access. Those bullets sit with the transition tasks, ahead of the Plan subsection. | [cite:1] |
Read “Webex Calling” in nbedetf as multi-tenant. Dedicated Instance is a different architecture and lives in T5-R02. [cite:1]
The configuration workflow’s feature catalog (auto attendant, hunt group, call queue, and the user feature list) is dated March 20, 2025. Use it as a map of objects, then confirm each object in its own article. re-check [cite:2]
The guide says customers with these requirements should consider keeping call control on premises: phone models Webex Calling does not support, complex on-premises integrations, a complex dial plan or highly granular classes of service, restrictive or unreliable internet, stringent data-privacy policies, a compliance need for on-premises or in-country recording, third-party integrations without a Webex Calling alternative, and contact-center integrations that are not moving to the cloud yet. [cite:1]
04 · Ecosystem
Ecosystem and sister technologies
Glossary
- Webex Calling (in nbedetf)
- The multi-tenant cloud call service. Endpoint registration and call routing live in that cloud. [cite:1]
- Control Hub
- The management portal for the bundled offer, reached at admin.webex.com. re-check [cite:2]
- Local gateway
- Enterprise or partner edge that provides PSTN and connects a legacy PBX, including Unified CM. [cite:1] re-check [cite:2]
- Trunk
- The Webex Calling connection to the premises. It terminates on a local gateway or a supported device. [cite:3]
- Route group
- Trunks grouped for distribution or redundancy. [cite:3]
- Survivability Gateway
- Local IOS-XE gateway that endpoints use when the cloud path is down. Detail is T2-R07. [cite:1]
- PPDIO
- Prepare, Plan, Design, Implement, Optimize, as the migration guide uses those phases. [cite:1]
Mind map
Mermaid source (not rendered)
mindmap
root((Calling))
Control Hub
Local gateway
Cloud PSTN
Directory
Survivability
Sister-technology matrix
| Sister | What it is | Why it matters here | Config touchpoint | Typical failure | Cite |
|---|---|---|---|---|---|
| Directory | Directory Connector on a domain-joined Windows machine, or the Entra ID Wizard. | Users have to exist before lines do. T1-R02 is the identity room. | The wizard replaces the connector when the directory is Entra ID. | Keeping Directory Connector after the directory moved. | [cite:1] |
| Locations | The container that receives a gateway and a PSTN choice. | T1-R04 creates the location. This room places calling on it. | Plan-phase emergency address, users, internet, PSTN. | A location with no PSTN decision. | [cite:1] |
| Local gateway / CUBE | IOS-XE or a certified third-party SBC. | Premises PSTN and Unified CM interworking. | Control Hub assigns the gateway, then you apply the parameters on CUBE. | Expecting cloud PSTN to serve premises-originated calls. | [cite:1] [cite:3] |
| Dial plan | Global for all users. | Patterns and prefixes are T2-R03. | Trunks and route groups. | Teaching illegal patterns in this room. | [cite:3] |
| Emergency | The migration section lists the emergency response address among location details. | E911 design is a sister of the location, not a feature code. | Location data gathered with users, internet, and PSTN. | Cutting over without that address in the worksheet. | [cite:1] |
| Webex App | Windows, Mac, Android, and iOS, registered to Webex Calling. | The soft client is an endpoint of the cloud, not a Jabber CTI client. | User license and registration. | Leaving Jabber as the only client in the after picture. | [cite:1] |
| Recording and contact center | On-premises recording and a contact center that is not moving are named reasons to stay on Unified CM. | Those workloads can block a full move. | Design phase, stay-versus-move. | Assuming every UC app moves because calling did. | [cite:1] |
| Partner support | The workflow says tier 1 partner support, then Cisco. | The operating model is part of the architecture. | Partner, then Cisco TAC. | Opening a Cisco case before the partner path the article names. | [cite:2] |
Integration edges
| From | To | Mechanism | What moves | Cite |
|---|---|---|---|---|
| Webex App | Webex Calling | Direct registration | The soft client on Windows, Mac, Android, iOS | [cite:1] |
| Control Hub | Location | Gateway assignment | Local gateway parameters later applied on CUBE | [cite:2] |
| Webex Calling | Premises | Trunk | Calls toward a local gateway or supported device | [cite:3] |
| Local gateway | PSTN or PBX | Interconnect | Premises PSTN and Unified CM calling | [cite:1] |
| Route group | Trunks | Distribution or redundancy | Which trunk carries the call | [cite:3] |
| Directory | Control Hub | Directory Connector or Entra ID Wizard | Users | [cite:1] |
| Cloud PSTN | Webex Calling users | Cisco Calling Plan or Cloud Connect | PSTN without on-premises equipment | [cite:1] |
| Outage | Survivability Gateway | Local IOS-XE fallback | Basic calling while the cloud path is down | [cite:1] |
Cross-platform bridges
Future-integration hooks
- The guide names three help paths: Webex migration tools in Control Hub (self-service), certified migration providers, and Webex Setup Assist (Cisco-led). [cite:1]
- Preferred Architecture details stay in Cisco’s Preferred Architecture document. Diagrams that were not in the retrieved help article stay out of this room.
- Canon planning: keep a one-page before/after for each site: registration target, PSTN choice, and whether the contact center moves.
Ecosystem troubleshooting
| Symptom | Likely sister-system cause | Check | Fix | Cite |
|---|---|---|---|---|
| Premises users expect Cisco Calling Plan to place their calls | Cloud PSTN is for Webex Calling users. | Where the call starts. | Premises-originated PSTN uses the local gateway path. T2-R03 holds the routing sentences. | [cite:3] |
| Entra ID users are still planned on Directory Connector | The guide says Entra ID customers use the Entra ID Wizard instead. | Which directory the org uses. | Follow the wizard path in T1-R02. | [cite:1] |
| A site with a contact center is drawn as a full move | A contact center that is not moving is a named reason to keep Unified CM. | The design-phase stay list. | Split calling users from the contact-center decision. | [cite:1] |
05 · Flow
From plan data to a registered gateway
| Step | From | To | Protocol | Notes | Cite |
|---|---|---|---|---|---|
| 1 | Current UC | Inventory | Prepare | Unified CM, Expressway pairs, optional CMS/CMM/TMS, optional Unity Connection. | [cite:1] |
| 2 | Location | Migration worksheet | Listed details | Emergency response address, number of users, internet access, PSTN access. | [cite:1] |
| 3 | Directory | Control Hub | Connector or wizard | Entra ID uses the wizard. | [cite:1] |
| 4 | Admin | Control Hub | HTTPS admin.webex.com | First-time calling setup, users, numbers, services. re-check | [cite:2] |
| 5 | Control Hub | Location | Gateway assignment | Parameters are then configured on CUBE. re-check | [cite:2] |
| 6 | CUBE | Webex Calling | Registration from those steps | The workflow says those steps register the local gateway with the cloud. re-check | [cite:2] |
| 7 | Webex App | Webex Calling | Direct registration | Windows, Mac, Android, iOS. | [cite:1] |
| 8 | Cloud | PSTN or Unified CM | Trunk to local gateway | Route groups when more than one trunk is used. | [cite:3] |
06 · Config
Click paths and the order around them
- Sign in at admin.webex.com. The workflow calls Control Hub the management portal for the bundled calling offer. re-check [cite:2]
- Complete first-time calling setup: users, numbers, and services. The same article says you can cross-launch to the Calling Admin Portal. re-check [cite:2]
- Choose PSTN per location: premises through a local gateway, Cisco Calling Plan, or Cloud Connect. Cloud options in the migration guide need no on-premises equipment. [cite:1]
- For a local gateway, assign it to the location in Control Hub, then configure the parameters Control Hub provides on CUBE. re-check [cite:2]
- Build trunks and route groups when the premises connection needs distribution or redundancy. Dial-plan patterns stay in T2-R03. [cite:3]
- Register Webex App directly to Webex Calling on the platforms the guide names. [cite:1]
- If the directory is Entra ID, use the Entra ID Wizard rather than Directory Connector. [cite:1]
- Record the location details the migration section names: emergency response address, number of users, internet access, and PSTN access. [cite:1]
Screenshot placeholder. The paths above are the articles.
07 · Limits
Values the articles state
| Item | Value | Source | Verified? |
|---|---|---|---|
| Meaning of Webex Calling in the migration guide | Always the multi-tenant service | [cite:1] | Quoted. Header January 14, 2026. |
| Local gateway platforms named | IOS-XE ISR 1100 and 4000, Catalyst 8200 and 8300, Catalyst 8000V, certified third-party SBCs | [cite:1] | Quoted |
| Webex App platforms | Windows, Mac, Android, iOS | [cite:1] | Quoted |
| Cloud PSTN equipment | Cisco Calling Plan and Cloud Connect require no on-premises equipment | [cite:1] | Quoted |
| Who cloud PSTN serves | Webex Calling users | [cite:3] | Quoted from the trunks article. Header date not restated in this pass. re-check |
| Workflow header | March 20, 2025 | [cite:2] | re-check Older than 12 months. |
| Help paths | Control Hub migration tools, certified providers, Webex Setup Assist | [cite:1] | Quoted |
08 · Troubleshooting
Eight architecture mismatches
| Symptom | Likely cause | Evidence | Fix | Cite |
|---|---|---|---|---|
| The design treats Dedicated Instance as the guide’s Webex Calling | nbedetf uses Webex Calling for the multi-tenant service. | The guide’s opening definition. | Put Dedicated Instance in the T5 track. | [cite:1] |
| Jabber is still the after-state client | The before table registers Jabber to Unified CM. The after state registers Webex App to Webex Calling. | Which client the design names. | Draw Webex App on the cloud side. | [cite:1] |
| No gateway and no cloud PSTN | PSTN is either a local gateway or a cloud option. | The location’s PSTN choice. | Pick one of the named options. | [cite:1] |
| CUBE is configured before Control Hub assigns it | Control Hub assigns the gateway to a location and then provides the parameters. | Whether the location assignment exists. | Assign first, then apply the parameters. re-check | [cite:2] |
| A single trunk is called a route group | A route group is trunks used together for distribution or redundancy. | How many trunks exist. | Use the trunk until a second path is required. | [cite:3] |
| Directory Connector is specified for an Entra ID org | The guide points those customers at the Entra ID Wizard. | The directory product. | Use the wizard. | [cite:1] |
| Phones Webex Calling does not support are in the move list | Phone models not supported by Webex Calling are a named reason to consider keeping call control on premises. | The endpoint inventory. | Keep those phones on Unified CM or replace them. The guide does not list model numbers in that bullet. | [cite:1] |
| The worksheet has users and no emergency address | The migration section lists the emergency response address with the number of users, internet access, and PSTN access. | The location worksheet. | Add the address to those location details. | [cite:1] |
09 · Self-question ladder
Twelve rungs
L0What does Webex Calling mean in the migration guide?
The multi-tenant cloud call service. [cite:1]
L0Where do you administer the bundled offer?
Control Hub at admin.webex.com. re-check [cite:2]
L1What registers to Unified CM in the before picture?
Desk, Room, and Board devices, IP phones, and Jabber. [cite:1]
L1What do the Expressway pairs do in that picture?
Mobile and remote access, and business-to-business. [cite:1]
L2What does the local gateway bridge?
PSTN for cloud-registered endpoints, and calls between Unified CM-registered and cloud-registered endpoints. [cite:1]
L2Which cloud PSTN options need no on-premises equipment?
Cisco Calling Plan and Cloud Connect for Webex Calling. [cite:1]
L3Where does a trunk terminate?
On a local gateway or another supported device. [cite:3]
L3Who does cloud PSTN serve?
Webex Calling users. [cite:3]
L4Which directory tool does the guide name for Entra ID?
The Entra ID Wizard, instead of Directory Connector. [cite:1]
L4Which location details does the migration section list?
Emergency response address, number of users, internet access, and PSTN access. [cite:1]
L5Name one reason the guide gives for keeping call control on premises.
Phone models Webex Calling does not support, complex on-premises integrations, a complex dial plan or highly granular class of service, restrictive or unreliable internet, stringent data privacy, on-premises or in-country recording, a third-party integration without a Webex Calling alternative, or a contact-center integration that is not moving yet. [cite:1]
L5Why is the March 20, 2025 workflow marked?
That header is older than 12 months, so its feature list is re-check until the article is read again. [cite:2]
10 · Lab
Paper architecture, no production trunk
11 · Quiz
Twelve questions
In nbedetf, Webex Calling means which service?
Answer
The multi-tenant cloud call service. [cite:1]
What does the local gateway connect besides PSTN?
Answer
Calls between Unified CM-registered endpoints and cloud-registered endpoints. [cite:1]
Which IOS-XE platforms does the guide name for a local gateway?
Answer
ISR 1100 and 4000, Catalyst 8200 and 8300, and Catalyst 8000V, plus certified third-party SBCs. [cite:1]
Where does Webex App register?
Answer
Directly to Webex Calling. [cite:1]
What is a route group?
Answer
Trunks used for distribution or redundancy. [cite:3]
Who is cloud PSTN for?
Answer
Webex Calling users. [cite:3]
The customer directory is Microsoft Entra ID.
Answer
Use the Entra ID Wizard instead of Directory Connector. [cite:1]
What does Control Hub hand you for CUBE?
Answer
Parameters to configure on the gateway after it is assigned to a location. re-check [cite:2]
Name the three migration help paths.
Answer
Webex migration tools in Control Hub, certified migration providers, and Webex Setup Assist. [cite:1]
What does a Survivability Gateway do at this altitude?
Answer
It is a local IOS-XE fallback during an outage. [cite:1]
Why is 0xvuwab marked re-check?
Answer
Its header is March 20, 2025. [cite:2]
Draw registration before and after, and the PSTN bridge.
Answer
Before: phones and Jabber on Unified CM, Expressway for MRA and B2B. After: Webex App on Webex Calling. Local gateway for PSTN and for calls that still touch Unified CM. [cite:1]
12 · Audio
Slots for Studio
Transcript slot
Studio fills this.
Transcript slot
Studio fills this.
Transcript slot
Studio fills this.
13 · Interview
Oral answers
30 seconds. Webex Calling in the migration guide is the multi-tenant cloud. Phones register there. A local gateway is the bridge for PSTN and for calls that still involve Unified CM. Cisco Calling Plan and Cloud Connect need no gateway.
2 minutes. Before the move I inventory Unified CM, the Expressway-C and Expressway-E pair, and optional meeting servers and Unity Connection. Desk, Room, Board, IP phones, and Jabber are on Unified CM. After the move, Webex App on Windows, Mac, Android, and iOS registers to the cloud. Control Hub at admin.webex.com assigns a local gateway to a location and hands me CUBE parameters. A trunk terminates on that gateway. A route group is how I put trunks together. Dial plans are global, and the pattern rules live in the dial-plan room. If the directory is moving to Entra ID, I use the wizard. The migration section also lists the emergency address, the number of users, internet access, and PSTN access.
30 seconds, what stays. Phone models Webex Calling does not support, a complex dial plan, unreliable internet, on-premises recording requirements, and a contact center that is not moving yet are reasons the guide gives for considering on-premises call control.
2 minutes, what I will not merge. I will not teach Dedicated Instance from this guide. I will not let cloud PSTN serve a call that starts on the premises. I will not quote the March 20, 2025 feature catalog as current without a re-check. Preferred Architecture drawings stay in Cisco’s document until I have read them.
What you will say about help. The three paths are self-service migration tools in Control Hub, a certified migration provider, and Cisco-led Webex Setup Assist.
14 · Citations
- Migrate Unified CM to Webex Calling, introduction — help.webex — article nbedetf — help.webex.com article nbedetf — header January 14, 2026 — retrieved 2026-10-14. Multi-tenant meaning, component list, before-and-after, local gateway platforms, cloud PSTN without on-premises equipment, Entra ID Wizard, Survivability Gateway, PPDIO definitions, location details in the migration section, reasons to consider keeping call control on premises, three help paths.
- Webex Calling Configuration Workflow — help.webex — article 0xvuwab — help.webex.com article 0xvuwab — header March 20, 2025 — retrieved 2026-10-14. re-check. admin.webex.com, first-time setup, local gateway assignment and CUBE parameters, tier 1 partner support then Cisco.
- Configure trunks, route groups, and dial plans for Webex Calling — help.webex — article n0xb944 — help.webex.com article n0xb944 — retrieved 2026-10-14. Header date not restated in this pass. re-check. Trunk terminates on a local gateway or supported device. Route group for distribution or redundancy. Cloud PSTN for Webex Calling users. Dial plans are global. Pattern language is taught in T2-R03.
15 · Re-engineer later
- Open questions: the current header on 0xvuwab, and the header date on n0xb944.
- Facts still TODO-verify: 0. Workflow sentences and the trunks header are re-check.
- Assets missing: architecture screenshot, audio, Preferred Architecture plates after that document is read.
- Ideas for v1.0: a before/after registration card next to the PSTN choice.
- Next review: when nbedetf changes the multi-tenant sentence or the gateway platform list.
Sources and go deeper
Checked links were opened this month. A confirm row has no address because that page was not opened.
- Wikipedia Webex (Wikipedia) last checked 2026-10
- Vendor doc Webex Help Center last checked 2026-10
- DevDocs Webex developer documentation last checked 2026-10
- DevDocs Webex developer getting started last checked 2026-10
- Community Webex community last checked 2026-10
- SRND Cisco Collaboration design zone last checked 2026-10
- RFC RFC 3261 SIP: Session Initiation Protocol last checked 2026-10
- Port table IANA service name and port number registry last checked 2026-10
- Port table Port reference for Webex Calling last checked 2026-10
- RFC RFC 3263 Locating SIP Servers last checked 2026-10
- RFC RFC 3264 An Offer/Answer Model with SDP last checked 2026-10
- Wikipedia Session Initiation Protocol (Wikipedia) last checked 2026-10
- RFC RFC 3550 RTP last checked 2026-10
- RFC RFC 3711 SRTP last checked 2026-10
- RFC RFC 4566 SDP last checked 2026-10
- RFC RFC 4733 RTP payload for DTMF last checked 2026-10
- Wikipedia Real-time Transport Protocol (Wikipedia) last checked 2026-10
- Release notes What's new in Webex Calling last checked 2026-10
- Vendor doc help.webex.com article nbedetf last checked 2026-10
- Vendor doc help.webex.com article 0xvuwab last checked 2026-10
- Vendor doc help.webex.com article n0xb944 last checked 2026-10
sources.json for this page.