Source record · tier 2 current vendor documentation

Prepare to migrate from Unified CM to Webex Calling

Publisher: Cisco Systems, Inc. (Webex Help Center)
URL: https://help.webex.com/en-us/article/4yz2zd/Prepare-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 positions the built-in Webex Calling Auto Attendant as the destination for Unity Connection call handler and auto-attendant functionality, and names the Control Hub tool 'Migrate Features from Unified CM' as supporting migration of Unity Connection configurations to Webex Calling auto attendants. in context
There is no native way to migrate existing Unity Connection voicemail messages or greetings into Webex Calling voicemail. in context
Cisco states that some third-party partner migration tools can migrate some Unity Connection voicemail data, without naming the tools or the data covered. in context
Webex Calling cannot integrate with a premises voicemail system such as Unity Connection or Unity Connection Express. in context
Webex Calling supports shared voicemail and fax mailboxes. in context
Voicemail is built natively into the Webex Calling offer. in context
Cisco says users moved to Webex Calling can search the Webex directory for enterprise users still on Jabber or Unified CM. in context
Cisco says one-way latency between the Local Gateway and the Webex Calling access SBC should not exceed 100 ms. in context
Cisco states a single registration-based Local Gateway supports up to 250 concurrent calls, and certificate-based connectivity can support more, up to 6500 depending on connectivity type and SBC model. in context
Cisco recommends moving users together when they depend on each other through BLF monitoring, the same hunt pilot or group, shared lines, the same pickup group, shared call-park numbers, intercom or admin/exec relationships. in context
There is no native way to migrate existing Unity Connection voicemail messages or greetings to Webex Calling voicemail. in context
A Control Hub location can be assigned only one PSTN option: Cisco Calling Plans, Cloud Connect, or on-premises PSTN via Local Gateway. in context
Webex Calling cannot integrate with a premises-based voicemail system such as Unity Connection or Unity Connection Express. in context
During coexistence an organization will likely run two voicemail systems, Webex Calling native voicemail for migrated users and Unity Connection for users still on Unified CM, since Webex Calling cannot use Unity Connection. inferred in context
The stated reason for moving to the Webex App first is to give users time to get used to the new app while they are still on on-premises Unified CM calling. in context
Depending on the Jabber deployment modes in use (IM-only, phone-only or full UC), a Webex Calling migration may also need to move Messaging and/or Meetings workloads from Jabber to the Webex App. in context
The Webex App can be deployed in phone-only mode as a calling-only client, or as the full Webex Suite when messaging and/or meetings move to the app along with calling. in context
The Prepare guide recommends that users first move to the Webex App with Unified CM calling, then move to Webex Calling. It calls this option 1. in context
Before users are moved to Webex Calling, their Jabber clients must be transitioned to the Webex App. in context
Unified CM supports both the Webex App and Cisco Jabber as soft clients. in context
The Webex App is the only soft client supported by Webex Calling. in context
Cisco sizes Webex Calling throughput as the number of expected concurrent calls multiplied by the per-call bandwidth for the codec in use. in context
Cisco's Prepare guidance names CScan (cscan.webex.com) as the tool for assessing network quality, estimated call capacity and latency. in context
Cisco's bandwidth table uses 80 kbps per call for G.711 calls from a desk phone to the PSTN through a Local Gateway. in context
For Webex Calling calls over the internet, Cisco's migration Prepare guidance sets a jitter target of less than 10 ms. in context
For Webex Calling calls over the internet, Cisco's migration Prepare guidance sets a one-way latency target of less than 100 ms. in context
For Webex Calling calls over the internet, Cisco's migration Prepare guidance sets a packet loss target of 0.5% or less. in context
Cisco's bandwidth table uses 70 kbps per call for OPUS calls between the Webex App or a desk phone and the Webex App. in context
Cisco places network readiness and requirements in the Prepare phase of a Unified CM to Webex Calling migration, which comes before the Plan phase. in context
Cisco's Prepare guidance says to implement QoS in the on-premises environment to prioritize real-time traffic and keep it in place across switches, routers and firewalls. in context
Cisco's bandwidth table allows up to 1,500 kbps per call for H.264 video calls in Webex Calling. in context
The documented current-environment assessment in the Prepare phase covers licensing, locations and sites, device inventory and eligibility, users, PSTN connectivity, features and feature usage, Cisco integrations including Unity Connection, call recording, and third-party integrations. in context
Cisco directs administrators to deploy Cloud-Connected UC early in the transition project, ideally before or during the preparation phase. in context
Cisco recommends verifying during the Prepare phase which Unified CM registered phones are eligible to upgrade to Multiplatform firmware, so that ineligible phones can be replaced or an alternative plan identified before cutover. in context
Feature assessment is documented as two complementary inputs: static configuration analysed through Control Hub Migration Insights, and dynamic utilisation data from call detail records, registrations and call activity. in context
Cisco provides no native way to migrate existing Unity Connection voicemail messages or greetings into Webex Calling's native voicemail service. in context
Webex Calling cannot integrate with a premises-based voicemail system such as Unity Connection or Unity Connection Express. in context
Cisco states that some of its third-party partners' migration tools can migrate some Unity Connection voicemail data; it does not name the tools or say which data. in context
Webex Calling supports shared voicemail and fax mailboxes (voicemail groups). in context
Voicemail is built into the Webex Calling offer rather than supplied by a separate voicemail product. in context

Cite this source record

APA

WarmTransfer. (2026, September 16). Prepare to migrate from Unified CM to Webex Calling. WarmTransfer. https://warmtransfer.net/knowledge/sources/cisco-help-4yz2zd-prepare-migrate-ucm-wxc

BibTeX

@misc{warmtransfer-cisco-help-4yz2zd-prepare-migrate-ucm-wxc,
  title  = {Prepare to migrate from Unified CM to Webex Calling},
  author = {{WarmTransfer}},
  year   = {2026},
  url    = {https://warmtransfer.net/knowledge/sources/cisco-help-4yz2zd-prepare-migrate-ucm-wxc},
  note   = {Cisco Systems, Inc. (Webex Help Center), accessed 2026-09-16}
}