Cisco Unified Communications Manager Cloud and Hybrid Call/Message Routing
This domain tests how calls and messages move between on-premises UCM, Cisco-hosted UCM Cloud, and Webex. You need to distinguish the platforms, know which connector carries call signalling, and be able to trace a dialled digit string end to end.
Platforms and their routing models
- UCM Cloud: a dedicated Cisco-hosted UCM cluster with a full UCM dial plan, translation patterns, and SIP trunks to Cloud Connected PSTN.
- Webex Calling: multi-tenant, organized by locations, users, and numbers, with route groups, route lists, route plans, and dial plans. PSTN is Cisco Calling Plans, a Cloud Connected PSTN partner, or premises-based PSTN through a CUBE.
Hybrid Call Service Connect
A call connector on Expressway-C ties Webex App users to on-premises UCM. The user keeps a single business number, and outbound calls use the UCM dial plan and PSTN trunks rather than cloud PSTN. Requirements: supported UCM, registered Expressway-C, the hybrid call entitlement, enablement in Control Hub, and per-user assignment.
Tracing a call
Webex App sends the call to the cloud, the cloud hands it to the call connector, Expressway-C delivers it to UCM, and UCM applies its own dial plan and trunks.
Message routing
Messaging is cloud-hosted in Webex. Hybrid Message Service, which once kept messages on-premises with Exchange, is legacy and should not be designed into new deployments.
Worked example
A Webex App user dials extension 4100, a colleague on an on-premises UCM phone. The call goes from Webex App to the cloud, through the call connector and Expressway-C to UCM, where the dial plan matches 4100 as an internal extension and completes the call. If the user instead dialled an external number, UCM would route it out its own gateway, not through cloud PSTN. Reasoning: Hybrid Call Service Connect supplies call control, not PSTN.
Traps that cost marks
- Assuming Call Service Connect provides PSTN; it does not.
- Confusing the call connector with the calendar connector.
- Treating UCM Cloud as customer-managed infrastructure.
- Overlapping dial plans between cloud and on-premises that black-hole calls.