Source record · tier 2 current vendor documentation

Design to migrate from Unified CM to Webex Calling

Publisher: Cisco Systems, Inc. (Webex Help Center)
URL: https://help.webex.com/en-us/article/nqojzwt/Design-to-migrate-from-Unified-CM-to-Webex-Calling
Published: unknown
Updated: unknown
Accessed: 2026-09-16
HTTP status: 200
License: Cisco proprietary documentation, all rights reserved; no-redistribution; short excerpts and locators only

Source notes citing this source

Cisco lists coexistence dial plan requirements for Unified CM. They include +E.164, extension and abbreviated inter-site dialing to Webex Calling, forced on-net dialing in both directions, call-back from missed-call directories, and PSTN routing that depends on the PSTN strategy. in context
To avoid call loops, the inbound CSS on the Unified CM trunk from the Local Gateway should not have access to the Webex Calling partition. in context
Cisco's coexistence design uses translation pattern CSS inheritance ('Use Originator's Calling Search Space') to support dialing normalization patterns. in context
When Webex Calling needs abbreviated inter-site dialing but extensions overlap between locations, Cisco says to build an enterprise numbering plan by prefixing extensions with an access code and a site code. in context
Cisco's design guidance says to set the maximum unknown extension length in Webex Calling so that calls from on-premises call control into Webex Calling are classified correctly. in context
For Unified CM and Webex Calling coexistence, Cisco says a dedicated Webex Calling partition on Unified CM is required to create a differentiated class of service for calls that originate from Webex Calling. in context
In Cisco's coexistence design, when a +E.164 range moves to Webex Calling, an urgent route pattern matching that range is added to the Webex Calling partition on Unified CM. in context
Webex Calling location design calls for provisioning one DID for the voicemail number alongside the main location number. in context
Unified CM best-match routing means a +E.164 directory number still provisioned on Unified CM wins over a wildcarded +E.164 route pattern pointing to Webex Calling, so calls to that number stay on Unified CM. in context
Cisco says moving PSTN to a Cloud Connected PSTN provider at the start while keeping Unified CM during a phased migration adds complexity and risk, particularly in adapting existing Unified CM call routing. in context
To avoid call loops, the inbound calling search space on the Unified CM trunk from the Local Gateway must not have access to the Webex Calling partition. in context
During coexistence, calls between on-premises Unified CM users and Webex Calling users traverse the Local Gateway connection. in context
Cisco says the connection between on-premises and Webex Calling must be designed and sized for the expected number of concurrent calls and the required redundancy. in context
When creating a Webex Calling location, two DIDs must be provisioned: one as the location main number and one for the voicemail portal. in context
The Unified CM transition dial plan must support call-back from the missed calls directory to destinations on Webex Calling. in context
If extension ranges overlap across sites, Cisco says an enterprise numbering plan must be created by prefixing extensions with an access code and a site code. in context
Cisco lists porting challenges including coordinating port orders precisely, potential delays, and provider limits such as a cap on concurrent port requests. in context
Cisco says number porting can be done as a single coordinated cutover once the Webex Calling migration is complete, or incrementally per location as users move. in context
The transition dial plan must carry PSTN calls from Webex Calling via on-premises PSTN when that is used, and PSTN calls from Unified CM via Webex Calling when PSTN trunking for hybrid deployments is used. in context
Cisco describes retaining on-premises PSTN throughout the transition, with PSTN migrated per location as users move, as one option; Webex Calling users then use on-premises PSTN through the Local Gateway connection. in context
In Cisco's migration design, all site codes of all locations must be unique and have the same length. in context
Because a Unified CM directory number out-matches the wildcarded Webex Calling route pattern, a migrated user's number left configured on Unified CM would likely keep calls from Unified CM callers on Unified CM instead of reaching the user on Webex Calling. inferred in context
In Cisco's migration design, no extension range may start with the inter-site steering digit or the PSTN steering digit. in context
The Unified CM transition dial plan must also support abbreviated inter-site dialing and forced on-net dialing from Unified CM to Webex Calling. in context
During the transition the Unified CM dial plan must support +E.164 dialing to Webex Calling and extension dialing to Webex Calling, intra-site and also inter-site when extension ranges are unique. in context
Cisco's coexistence design adds a Webex Calling partition to the Unified CM dial plan containing +E.164 route patterns for all Webex Calling destinations. in context
In the reverse direction the transition dial plan must support forced on-net dialing and inter-site extension dialing from Webex Calling to Unified CM. in context
Cisco says all customers should deploy at least the basic emergency calling configuration, which requires at least one customer-owned +E.164 number assigned to each location. in context
Cisco says to enable 'Allow extension dialing between locations' only if all extensions within the organization are unique. in context
Webex Calling extension length is one fixed organization-wide setting of 2 to 10 digits, so all extensions in the deployment have the same length. in context
During a Unified CM to Webex Calling migration, calls between on-premises users and Webex Calling users use the Local Gateway connection. in context
Cisco says the connection between on-premises and Webex Calling must be designed and sized for the expected number of concurrent calls and the required redundancy. in context
Migrating PSTN per location brings number-porting challenges: coordinating port orders precisely, possible delays, and provider caps on the number of concurrent port requests. in context
Cisco describes two PSTN strategies for the transition: move to a Cloud Connected PSTN provider at the start, or keep on-premises PSTN throughout and migrate PSTN location by location. in context
Abbreviated inter-site dialing in Webex Calling uses a location routing prefix (length and steering digit set organization-wide) with a unique site code configured per location. in context
Seven-digit dial strings on a Webex Calling device using the US dial plan overlap with seven-digit local PSTN dialing; Cisco suggests adding a padding digit to the numbering schema. in context
Cisco's design provisions two DIDs per Webex Calling location: one main number (for example for an auto attendant) and one for the voicemail portal. in context
For coexistence the Unified CM dial plan must support +E.164 dialing, extension dialing (intra-site and inter-site), abbreviated inter-site dialing and forced on-net dialing to Webex Calling. in context
Cisco's design puts +E.164 route patterns for all Webex Calling destinations into a dedicated Webex Calling partition on Unified CM. in context
Cisco's Design and Implement guides for the UCM-to-Webex-Calling migration do not cover the Jabber-to-Webex-App transition. That guidance is in the Prepare and Plan guides. inferred in context
Extension length in Webex Calling is a fixed global setting, so every extension in a Webex Calling deployment has the same length. in context
Four user provisioning methods are documented: manual assignment in Control Hub, automatic licence templates, bulk CSV upload, and API-based assignment, with automatic templates requiring valid phone numbers to already exist in the location. in context
Each Webex Calling location must be documented with extension ranges, DID ranges, PSTN steering digits, site code, main number, voicemail number, licence counts, busy-hour concurrent calls, country, time zone, language, contact details, address and emergency dispatchable location. in context
The design guidance presents three PSTN connectivity options for Webex Calling: Cisco Calling Plans, Cloud Connected PSTN providers, and on-premises PSTN through a Local Gateway. in context
Cisco recommends selecting the Webex Calling instance that gives the lowest signalling round-trip times for the largest number of users in the deployment, and notes that the region is difficult to change afterwards. in context
Cisco recommends single sign-on for user authentication in the migrated deployment, supporting SAML 2.0, OpenID Connect and Webex identity, with multiple identity providers supported for merged or decentralised organisations. in context
On the Unified CM side the documented dial plan design uses a single partition for +E.164 directory numbers with core routing based on +E.164 route patterns, and enables +E.164 dialling from Unified CM to Webex Calling alongside extension and abbreviated inter-site dialling. in context
Cisco's migration design guidance says to provision one DID for the voicemail number at each Webex Calling location. in context
Cisco's migration design guidance lists voicemail group use cases as a department or workgroup mailbox, a voicemail option for an auto attendant or hunt group, call queue overflow, and users who only need a voicemail box. in context

Cite this source record

APA

WarmTransfer. (2026, September 16). Design to migrate from Unified CM to Webex Calling. WarmTransfer. https://warmtransfer.net/knowledge/sources/cisco-help-nqojzwt-design-migrate-ucm-wxc

BibTeX

@misc{warmtransfer-cisco-help-nqojzwt-design-migrate-ucm-wxc,
  title  = {Design to migrate from Unified CM to Webex Calling},
  author = {{WarmTransfer}},
  year   = {2026},
  url    = {https://warmtransfer.net/knowledge/sources/cisco-help-nqojzwt-design-migrate-ucm-wxc},
  note   = {Cisco Systems, Inc. (Webex Help Center), accessed 2026-09-16}
}