CUCM to Webex Calling migration

Verified 2026-09-05 · 61 claims · sources tier 2–3 · 1 disputed

Also known as PPDIO, big bang, coexistence, flash-cut.

Unified CM to Webex Calling migration encompasses native assessment utilities, data conversion tools, device firmware transitions, and coexistence architectures 44​32. Cisco defines both flash-cut migrations and phased hybrid transitions that support dual call control across on-premises and cloud platforms 31​32.

Migration approaches and project lifecycle

Cisco defines 2 migration approaches: a flash-cut where all users and devices transition in 1 window before on-premises decommissioning, and a phased approach where groups migrate over an extended timeline 31. The phased architecture progresses across 3 architecture phases 32:

• Phase 0: Unified CM only on premises 32.
• Phase 1: Hybrid coexistence with dual call control split across Unified CM and Webex Calling 32.
• Phase 2: Fully cloud calling with all users hosted on Webex Calling 32.

Cisco explicitly allows organisations to remain indefinitely in the Phase 1 dual call control coexistence state without completing a transition to cloud calling 40. Cisco lists several business reasons to retain on-premises call control: unsupported phone models, complex dial plans or granular classes of service, complex integrations lacking cloud equivalents, unreliable internet connectivity, strict data privacy or ownership requirements, in-country or on-premises call recording mandates, third-party integrations lacking cloud alternatives, and contact centre integrations not yet transitioning to cloud 48.

The recommended project lifecycle spans 3 distinct phases 56:

• Pre-Migration: Organisation setup, licensing, user provisioning, network readiness, and software upgrades 56.
• Migration Prep: Feature definition, Unified CM data extraction, client and phone version planning, testing, and pilot execution 56.
• Migration Rollout and Decommission: Adoption, user and device migration, feature migration, and decommissioning the on-premises deployment 56.

Migration utilities and Control Hub tasks

Cisco provides a native migration utility family consisting of Migration Insights, devices and features migration from Unified CM, user and contact synchronisation, Unified CM data conversion, Enterprise-to-MPP phone firmware conversion, and Jabber to Webex App migration 44. Migration Insights is accessed in Control Hub under Services, Upgrades and Migrations as an assessment step to evaluate cloud calling migration 43.

The Unified CM data migration workflow is launched in Control Hub under Services, Upgrades and Migrations via the tile Migrate Unified CM to Webex Calling 36. The devices and features migration tool is reached under Services, Updates and Migrations in the Migration utilities section on the Migrate features from Unified CM card 37. Sources disagree on the Control Hub navigation path: 2 current Cisco help articles give conflicting menu labels, with the Unified CM data migration article citing Services then Upgrades and Migrations, and the devices and features migration article citing Services then Updates and Migrations 34.

Running migration tasks and importing data involves specific prerequisites and limits:

• A single Unified CM to Webex Calling migration task can migrate at most 1000 users and 1000 devices, requiring larger estates to run multiple tasks 55.
• All Unified CM end users must be provisioned in Webex via Cisco Directory Connector or another mechanism prior to running a migration task 47.
• Phones migrating from Unified CM must run Phone Load version 14.1 or later 46.
• The Unified CM .tar file uploaded to the devices and features migration tool is capped at 350 MB 53.
• An optional Cisco Unity Connection export generated with the CallHandlerDataDump tool can be uploaded as a .zip file up to 2 GB 57.
• The WebexSamples GitHub repository ucmtowxc-migrationapi is archived with a last push date of 3 July 2023, carrying no description or licence 6.

Hybrid coexistence and call routing

In target architectures, Webex Calling provides cloud call control, Cisco Directory Connector or the Entra ID wizard manages identity synchronisation, a Local Gateway handles PSTN routing and Unified CM interoperation, and a Survivability Gateway supplies outage survivability 54. When using Cisco Calling Plan or Cloud Connect, no on-premises equipment is required 54.

During coexistence, a Local Gateway can simultaneously provide PSTN connectivity and an interconnect to on-premises call control, which may remain in permanent use 29. Over a single route group or trunk, Webex Calling dial plans separate calls destined for on-premises Unified CM (routed as enterprise calls) from other destinations (routed as PSTN calls) 28.

In Cisco's documented coexistence configuration, the Local Gateway segments traffic by port: calls arriving from Unified CM on port 5060 route to the PSTN, while calls arriving on port 5065 route to Webex Calling 30. This requires configuring the Unified CM SIP trunk security profile incoming port to 5065 30. Additionally, abbreviated dialling (such as 4 digits) is preserved for partially migrated locations by configuring an on-premises extension setting that routes unmatched extensions between 2 and 10 digits to a designated trunk or route group 27.

Endpoint and client transitions

Webex Calling supports a smaller subset of desk phones than Unified CM, restricted to the Cisco 6800, 7800, 8800, and 9800 series 20.

The Cisco Cloud Upgrader converts Enterprise firmware phones on Unified CM or HCS to Multiplatform firmware and applies the calling service enablement licences 25​26. These migration licences are generated via a Cisco web portal, or the firmware and licences can be hosted locally on Unified CM 24​23.

Device eligibility can be checked in Control Hub using the Migrate Your Phone to Webex Calling tool, where selecting "Generate device license only" evaluates eligibility without adding devices 35. When an eligibility check returns "Unknown", administrators resolve the status by checking the product ID and version ID on the physical label or by running an IP Phone Readiness Tool against Unified CM 58. Cisco states that the IP Phone Readiness Tool it points to is not an official Cisco tool and is not supported by Cisco TAC, carrying best-effort support only while being free to use 60.

Specific hardware caveats apply to 8800 series models:

• Older 8800 models with hardware version VID 14 or earlier register with Webex Calling but may experience performance issues due to hardware limitations 15.
• The 8845, 8865, and 8865NR have reached end of sale, and Cisco does not recommend migrating them 16​19.
• The 8845, 8865, and 8875 are listed as supported personal video phones with Webex Calling 18​19.

For soft clients, Webex App is the only soft client supported on Webex Calling, whereas Unified CM supports both Webex App and Jabber 11. Cisco recommends transitioning users to Webex App while still registered to Unified CM calling before performing the cutover to Webex Calling 49.

See also

• See also Unified CM release trains and lifecycle dates.
• See also Webex Calling architecture and deployment models.
• See also Webex Calling Dedicated Instance applicability.
• See also Local Gateway design and configuration.
• See also Identity SSO and directory provisioning for UC.
• See also Webex Calling supported devices and MPP firmware.
• See also Jabber to Webex App migration.
• See also Unified CM Bulk Administration Tool export formats.
• See also Cisco Unity Connection voicemail and migration.
• See also Webex Calling license types and entitlements.
• See also Webex Calling calling features and feature parity vs UCM.
• See also Webex Calling locations and number management.
• See also Migrating Unified CCE or Unified CCX to Webex Contact Center.
• See also Network readiness assessment for cloud calling.
• See also Webex Contact Center platform generations and predecessors.
• See also The Webex Contact Center Classic voice media platform.
• See also Voice POP bridge telephony lifecycle in Webex Contact Center.
• See also Help centre articles that serve the wrong document.
• See also Mislabelled and defective documents across the Cisco help estate.
• See also Help centre article type metadata as a retrieval discriminator.

Applicability

Across the claims in this article, the evidence covers Cisco Webex Calling, Cisco IP Phone 7800 Series, and Cisco IP Phone 8800 Series across multi-tenant, dedicated instance, hcs, and hybrid-webex-calling-with-onprem-unified-cm deployments, verified as of 2026-09-04. Unified CM endpoints migrating to Webex Calling must be on Phone Load version 14.1 or later 46. Older 8800 series hardware versions VID 14 or earlier have documented performance caveats 15. The WebexSamples migration API repository has been archived since 3 July 2023 6.

What remains uncertain

Sources disagree on the exact Control Hub navigation path to reach migration tools, with documentation conflicting between "Services > Upgrades and Migrations" and "Services > Updates and Migrations" 34.

The following items are not covered by any claim in this article:

• Webex Calling licence types entitlements and what each includes is not covered by any claim in this article.
• A feature-by-feature parity matrix between Unified CM and Webex Calling is not covered by any claim in this article.
• Which PSTN type changes are self-service vs manual vs unsupported is not covered by any claim in this article.
• The Plan, Design, Implement, and Operate chapters of the transition deployment guide are not covered by any claim in this article.
• The per-endpoint Webex Calling administration API reference is not covered by any claim in this article.
• The Port Reference Information document listing required IP ranges and ports is not covered by any claim in this article.
• What the CX Essentials licence covers and how it differs from Contact Center licensing is not covered by any claim in this article.
• The minimum Unified CM platform release supported by the Control Hub migration tool is not covered by any claim in this article.

11 claims on this topic await human review and are not used in this article.

WarmTransfer. (2026, September 5). CUCM to Webex Calling migration. WarmTransfer. https://warmtransfer.net/knowledge/cucm-to-webex-calling

@misc{warmtransfer-cucm-to-webex-calling,
  title  = {CUCM to Webex Calling migration},
  author = {{WarmTransfer}},
  year   = {2026},
  url    = {https://warmtransfer.net/knowledge/cucm-to-webex-calling},
  note   = {Verified 2026-09-05}
}