Telephony during a UCCX to Webex Contact Center migration

See also

Sources

1. 1
   Webex Contact Center documents five ways to deliver a call to an agent: PSTN interconnectivity with a DID or mobile number, Webex Calling registered endpoints such as MPP devices and the Webex App, WebRTC in the agent desktop, premises PBX or premises PSTN connectivity, and Microsoft Teams agents reached over Local Gateway direct SIP routing.

   Set up voice channels for Webex Contact Center · section "Agents Connection" · Checked 2026-09-22
2. 2
   The 2021 transition guide sizes the internet path to Webex Contact Center as expected concurrent calls multiplied by 80 kbps, and notes that the formula excludes video and excludes Management Portal, Analyzer, Agent Desktop and third-party cloud application traffic.

   Contact Center: Transitioning from Unified Contact Center Express to Webex Contact Center Deployment Guide · pre-transition step 4, "Perform network readiness assessment", bandwidth calculation · Checked 2026-09-22
3. 3
   The Cisco Webex Calling Plan option for Webex Contact Center is documented as currently available for Webex Contact Center trials and in regions where Cisco supports the service or inbound toll-free numbers.

   Set up voice channels for Webex Contact Center · section "Cisco Webex Calling Plan" · Checked 2026-09-22
4. 4
   Webex Calling Cloud Connected PSTN provides PSTN connectivity in over 65 countries through Certified Calling Providers, and requires a relationship with an authorised Cloud Connected PSTN partner for activation and billing.

   Set up voice channels for Webex Contact Center · section "Webex Calling Cloud Connected PSTN (Cloud Connect, CCP, or CCCP)" · Checked 2026-09-22
5. 5
   Webex Contact Center PSTN purchased from Cisco as a bundle is offered to customers in the contiguous United States and Canada and does not support international dialing.

   Set up voice channels for Webex Contact Center · section "Webex Contact Center PSTN" · Checked 2026-09-22
6. 6
   Cisco Live 2024 gave the certificate-based Local Gateway trunk capacity as up to 6,500 concurrent calls and the registration-based trunk as up to 250, with TLS for SIP and SRTP for media on both.

   BRKCCT-2723 (Cisco Live session deck; exact session title not extractable from the file) · session BRKCCT-2723, Local Gateway trunk authentication slides · Checked 2026-09-22
7. 7
   Webex Contact Center requires G.711 uLaw or G.711 aLaw on the PSTN leg.

   Set up voice channels for Webex Contact Center · section "PSTN Media and Signaling Requirements for Webex Contact Center", codec row · Checked 2026-09-22
8. 8
   Webex Contact Center and Webex Calling share a global network of edge access services for routing calls into the Webex cloud.

   Webex Contact Center Architecture · section on PSTN and Webex Calling integration · Checked 2026-09-22
9. 9
   The country of operation selected for Webex Contact Center in the services setup wizard cannot be changed after the administrator confirms it.

   Get started with Webex Contact Center · section "Services set up wizard", Contact Center step · Checked 2026-09-22
10. 10
    The UCCX-performing-call-distribution model requires an outgoing CUBE dial-peer matching the pilot extension and forwarding to the Webex Contact Center vPOP, an incoming dial-peer for agent extension routing, and a Unified CM route pattern with an E.164 dialled number whose partition is reachable from the UCCX CTI route point calling search space.

    Contact Center: Transitioning from Unified Contact Center Express to Webex Contact Center Deployment Guide · section "UCCX performing call distribution", configurations needed on your on-premises servers · Checked 2026-09-22
11. 11
    The transition guide documents a second hybrid model, titled CUBE performing call distribution, in which the CUBE rather than UCCX makes the initial routing decision and directs calls either to on-premises UCCX or to cloud Webex Contact Center.

    Contact Center: Transitioning from Unified Contact Center Express to Webex Contact Center Deployment Guide · section "CUBE performing call distribution" · Checked 2026-09-22
12. 12
    The 2021 transition guide states that when on-premises Unified CM call control is retained, the only supported codec between the on-premises CUBE and the Webex Contact Center vPOP is G.711, requiring 80 kbps per call.

    Contact Center: Transitioning from Unified Contact Center Express to Webex Contact Center Deployment Guide · pre-transition step 4, "Perform network readiness assessment" · Checked 2026-09-22
13. 13
    The TDM transition guide states that CUBE and optionally Cisco Unified SIP Proxy provide PSTN access in the transition architecture.

    Collaboration Transitions: Contact Center: Transitioning from Unified Contact Center Express to Webex Contact Center · architecture scope section · Checked 2026-09-22
14. 14
    To avoid making callers repeat information across the hand-off, the guide has the UCCX script write call variables to an external SQL database before the redirect, and has the Webex Contact Center flow retrieve them with an HTTP Request node against an on-premises database connector.

    Contact Center: Transitioning from Unified Contact Center Express to Webex Contact Center Deployment Guide · section "UCCX performing call distribution", configurations needed on your on-premises servers and on Webex Contact Center · Checked 2026-09-22
15. 15
    For Webex Contact Center integration with agents on Webex Dedicated Instance, Cisco directs administrators to build an audio codec preference list with G.711 uLaw first, then G.711 aLaw, then Opus.

    Webex Dedicated Instance Contact Center integration · section "Create audio codec preference list" · Checked 2026-09-22
16. 16
    Dedicated Instance to Webex Contact Center support requires certificate-based mTLS trunks; registration-based trunks are no longer supported for that integration.

    Webex Dedicated Instance Contact Center integration · section "Integrating Webex Contact Center (WxCC) and Webex Dedicated Instance" · Checked 2026-09-22
17. 17
    For Webex Contact Center with Dedicated Instance, Cisco documents two placements for agent phones: on Webex Calling multi-tenant with back-office users left on Dedicated Instance, or on Dedicated Instance with PSTN reached by Local Gateway or Cloud Connected PSTN.

    Webex Dedicated Instance Contact Center integration · section "Integrating Webex Contact Center (WxCC) and Webex Dedicated Instance", deployment options · Checked 2026-09-22
18. 18
    Webex Contact Center requires RFC 2833 DTMF on the PSTN leg.

    Set up voice channels for Webex Contact Center · section "PSTN Media and Signaling Requirements for Webex Contact Center", DTMF row · Checked 2026-09-22
19. 19
    Webex Calling supports +E.164 number formats by default when Cloud Connected PSTN or Local Gateway is used, and Control Hub stores PSTN numbers in +E.164 format.

    Set up voice channels for Webex Contact Center · section "+E.164 Globalized Call Routing Support for Multinational Contact Center Deployments" · Checked 2026-09-22
20. 20
    Webex Contact Center does not support SIP early media on the PSTN leg.

    Set up voice channels for Webex Contact Center · section "PSTN Media and Signaling Requirements for Webex Contact Center", SIP Early Media row · Checked 2026-09-22
21. 21
    Webex Contact Center does not support SIP Early Offer on the PSTN leg and does support SIP Delayed Offer.

    Set up voice channels for Webex Contact Center · section "PSTN Media and Signaling Requirements for Webex Contact Center", SIP Early Offer and SIP Delay Offer rows · Checked 2026-09-22
22. 22
    Entry points in Webex Contact Center are mapped to dialled numbers in Control Hub under Services, Contact Center, Tenant Settings, Voice, accepting single numbers or ranges, and a toll-free entry point mapping requires the corresponding Cisco PSTN entitlement.

    Set up voice settings for Webex Contact Center · sections on navigating to Voice settings and on inbound dial number to entry point mapping · Checked 2026-09-22
23. 23
    The 2021 transition guide enumerates five PSTN options: Cisco provided bundled PSTN, service provider, bring your own PSTN, bring your own PSTN with Local Gateway, and cloud connected PSTN with Webex Calling.

    Contact Center: Transitioning from Unified Contact Center Express to Webex Contact Center Deployment Guide · pre-transition step 6, "Understand PSTN options", options 1 to 5 · Checked 2026-09-22
24. 24
    The Cisco deployment guide Transitioning from Unified Contact Center Express to Webex Contact Center is dated September 2021 and runs to 74 pages.

    Contact Center: Transitioning from Unified Contact Center Express to Webex Contact Center Deployment Guide · cover page and document length · Checked 2026-09-22
25. 25
    Webex Calling PSTN trunking for hybrid calling scenarios lets an organisation connect an on-premises PBX to Cloud Connected Partner PSTN or Local Gateway PSTN, and Cisco presents phased cloud migration ahead of moving all users as one of its purposes.

    PSTN trunking for hybrid Webex Calling deployments · sections "How PSTN trunking works" and "PSTN on-premises migration scenario" · Checked 2026-09-22
26. 26
    In the UCCX-performing-call-distribution model the call is redirected to Webex Contact Center using an internal E.164 extension rather than a newly purchased service provider DID, which the guide presents as a cost saving.

    Contact Center: Transitioning from Unified Contact Center Express to Webex Contact Center Deployment Guide · section "UCCX performing call distribution", call flow description · Checked 2026-09-22
27. 27
    Webex Calling Local Gateway lets a customer keep its existing on-premises PSTN carrier and is described as providing access in over 140 markets globally, with the customer supplying and configuring the session border controller.

    Set up voice channels for Webex Contact Center · section "Webex Calling Local Gateway (LGWY)" · Checked 2026-09-22
28. 28
    A registration-based Local Gateway trunk supports up to 250 concurrent calls and is supported only on Cisco CUBE and Cisco Secure Routers, while a certificate-based trunk supports more than 250 concurrent calls and is supported on CUBE and on several third-party SBC platforms.

    Get started with Local Gateway · sections on registration-based trunks and certificate-based trunks · Checked 2026-09-22
29. 29
    After the media platform update, the dialled number field for VPOP customers accepts free-form E.164 input rather than a prepopulated value.

    Explain Notification for Media Platform Update · configuration changes section, VPOP customers · Checked 2026-09-22
30. 30
    The Control Hub article on migrating from Cisco Unified Contact Center Express to Webex Contact Center covers the discovery tool, configuration extraction and bulk upload, and carries no PSTN, SIP trunk, CUBE or codec guidance.

    Migrate Cisco Unified Contact Center Express to Webex Contact Center · full article as rendered on 2026-09-22 · Checked 2026-09-22
31. 31
    The 2021 transition guide sets network readiness thresholds of less than 150 ms end-to-end latency, less than 30 ms jitter and less than 1 percent packet loss.

    Contact Center: Transitioning from Unified Contact Center Express to Webex Contact Center Deployment Guide · pre-transition step 4, "Perform network readiness assessment" · Checked 2026-09-22
32. 32
    The transition guide does not document a path for transferring a call from Webex Contact Center back to UCCX during the hybrid phase; the hand-off it describes is one-directional.inferred

    Contact Center: Transitioning from Unified Contact Center Express to Webex Contact Center Deployment Guide · absence across sections "UCCX performing call distribution" and "CUBE performing call distribution" · Checked 2026-09-22
33. 33
    Webex Contact Center telephony options are greyed out after tenant provisioning and activation and cannot be changed without Cisco intervention.

    Set up voice channels for Webex Contact Center · section "PSTN Services", note following the option list · Checked 2026-09-22
34. 34
    Cisco documentation is inconsistent on whether Opus may appear anywhere on the path to Webex Contact Center: the voice-channel article requires every non-G.711 codec to be transcoded before reaching Webex Contact Center, while the Dedicated Instance integration article places Opus third on the codec preference list used for Webex Contact Center integration.disputed

    Webex Dedicated Instance Contact Center integration · section "Create audio codec preference list" read against cisco-help-nhy3codb-wxcc-voice-channel section "PSTN Media and Signaling Requirements for Webex Contact Center" · Checked 2026-09-22
35. 35
    In the Cisco transition deployment guide, agent devices continue to register to the on-premises Unified CM for call processing both during the hybrid phase and after the final transition.

    Contact Center: Transitioning from Unified Contact Center Express to Webex Contact Center Deployment Guide · section "Overview of this Transition Deployment Guide" · Checked 2026-09-22
36. 36
    The transition guide lists replacing bring-your-own PSTN with the Cisco bundled PSTN service as a post-transition step, not a prerequisite of the migration.

    Contact Center: Transitioning from Unified Contact Center Express to Webex Contact Center Deployment Guide · post-transition steps, item "Replace BYO PSTN with Cisco Bundled PSTN service" · Checked 2026-09-22
37. 37
    The transition guide lists replacing on-premises Unified CM with Webex Calling as a post-transition step, so the contact centre migration is designed to complete before the calling platform changes.

    Contact Center: Transitioning from Unified Contact Center Express to Webex Contact Center Deployment Guide · post-transition steps, item "Replace your Unified CM with Webex Calling" · Checked 2026-09-22
38. 38
    The 2021 Cisco transition deployment guide states that the PSTN option cannot be changed once it is configured for a tenant.

    Contact Center: Transitioning from Unified Contact Center Express to Webex Contact Center Deployment Guide · pre-transition step 6, "Understand PSTN options" · Checked 2026-09-22
39. 39
    The current Webex Contact Center voice-channel article presents four PSTN service options: Webex Contact Center PSTN, Webex Calling Cloud Connected PSTN, Webex Calling Local Gateway, and Cisco Webex Calling Plan.

    Set up voice channels for Webex Contact Center · section "PSTN Services" and its four subsections · Checked 2026-09-22
40. 40
    The next-generation media platform update added a PSTN Region field to entry point configuration, which VPOP customers set to match their VPOP region and Webex Calling customers set to choose where media is processed independently of the entry point hosting region.

    Explain Notification for Media Platform Update · configuration changes section, VPOP customers and Webex Calling customers · Checked 2026-09-22
41. 41
    Webex Contact Center expects a packetization timer of 20 ms in the SIP SDP on the PSTN leg.

    Set up voice channels for Webex Contact Center · section "PSTN Media and Signaling Requirements for Webex Contact Center", packetization row · Checked 2026-09-22
42. 42
    Webex Calling Regional Media for Cloud Connected PSTN keeps PSTN call traffic in a local data centre where the provider has a local regional connection, and falls back to the organisation's home region where it does not.

    Webex Calling Regional Media for Cloud Connected PSTN (CCP) · sections "Webex Calling Regional Media for Cloud Connected PSTN (CCP)" and "Available for" · Checked 2026-09-22
43. 43
    When Webex Contact Center reserves an agent in the hybrid phase it forwards the call to the on-premises CUBE, which extends it to Unified CM and in turn to the agent phone.

    Contact Center: Transitioning from Unified Contact Center Express to Webex Contact Center Deployment Guide · section "UCCX performing call distribution", agent reservation call flow · Checked 2026-09-22
44. 44
    The TDM transition guide assigns the CUBE two simultaneous roles in the hybrid deployment: PSTN access and Webex Contact Center interoperation, including letting Webex Contact Center reach Unified CM.

    Collaboration Transitions: Contact Center: Transitioning from Unified Contact Center Express to Webex Contact Center · considerations section, CUBE · Checked 2026-09-22
45. 45
    The companion Cisco guide Contact Center: Transitioning from Unified CCX to Webex CC is dated September 2021.

    Collaboration Transitions: Contact Center: Transitioning from Unified Contact Center Express to Webex Contact Center · cover page · Checked 2026-09-22
46. 46
    In the hybrid state described by the TDM transition guide, Webex Contact Center provides ACD, reserves the agent and routes incoming calls, while Unified CCX plays IVR prompts, reserves the agent and routes the call to the agent via Unified CM.

    Collaboration Transitions: Contact Center: Transitioning from Unified Contact Center Express to Webex Contact Center · hybrid step call-flow description · Checked 2026-09-22
47. 47
    A Webex Contact Center tenant must be connected to the PSTN and must have at least one method of delivering calls to agents.

    Set up voice channels for Webex Contact Center · section "PSTN Services", opening prerequisites · Checked 2026-09-22
48. 48
    The TDM transition guide requires bi-directional, redundant SIP over TLS trunks supporting G.711 toward Webex Contact Center.

    Collaboration Transitions: Contact Center: Transitioning from Unified Contact Center Express to Webex Contact Center · considerations section, CUBE and trunk requirements · Checked 2026-09-22
49. 49
    Any codec other than G.711, including G.729, iLBC and Opus, must be transcoded before the media reaches Webex Contact Center.

    Set up voice channels for Webex Contact Center · section "PSTN Media and Signaling Requirements for Webex Contact Center", transcoding note · Checked 2026-09-22
50. 50
    Cisco advises limiting the number of PSTN carriers involved in routing a call to Webex Contact Center to no more than two, and treats chained forwarding across multiple sequential carriers as unsupported because of the latency it introduces.

    Set up voice channels for Webex Contact Center · section "PSTN Call Forwarding Scenarios and Best Practices" · Checked 2026-09-22
51. 51
    The Cisco transition deployment guide structures a UCCX to Webex Contact Center move as two phases: a phase 1 hybrid deployment in which some queues and agents run on Webex Contact Center while the rest remain on UCCX, and a phase 2 purely cloud-hosted contact centre.

    Contact Center: Transitioning from Unified Contact Center Express to Webex Contact Center Deployment Guide · section "Overview of this Transition Deployment Guide" · Checked 2026-09-22
52. 52
    Where UCCX stays on customer premises and its Unified CM moves to Webex Dedicated Instance, the round-trip time between UCCX and the Dedicated Instance Unified CM must be less than 60 ms because JTAPI is latency sensitive.

    Webex Dedicated Instance Contact Center integration · section "Integrating UCCX and Webex DI", on-premises UCCX with Webex DI Unified CM · Checked 2026-09-22
53. 53
    In the first hybrid call-distribution model, the decision whether and when to send a given call to cloud Webex Contact Center is made inside the UCCX system.

    Contact Center: Transitioning from Unified Contact Center Express to Webex Contact Center Deployment Guide · section "UCCX performing call distribution" · Checked 2026-09-22
54. 54
    Cisco announced end of sale and end of life for version 12.5 and 12.6 of the on-premises contact center applications, covering UCCE, PCCE, UCCX and CVP, on 30 June 2025.

    Cisco Unified Contact Center Express - End-of-Life and End-of-Sale Notices · notice listing entry dated 30/Jun/2025 · Checked 2026-09-22
55. 55
    The June 2026 revision of the Webex Contact Center voice-channel article lists no vPOP, Voice POP Bridge or bring-your-own-PSTN-over-CUBE option among its PSTN services.

    Set up voice channels for Webex Contact Center · section "PSTN Services" and the full section list of the article · Checked 2026-09-22
56. 56
    At Cisco Live 2024 Cisco presented VPOP as the legacy telephony integration for Webex Contact Center, recommended Common Edge configuration for new customers, stated that new VPOP deployments would be by exception, and said new media regions would provide Common Edge support only with no new VPOP locations.

    BRKCCT-2723 (Cisco Live session deck; exact session title not extractable from the file) · session BRKCCT-2723 "How to connect PSTN to Webex Contact Center", VPOP transition slides · Checked 2026-09-22
57. 57
    As of the Cisco Live 2024 session on connecting PSTN to Webex Contact Center, Cisco had published no end-of-sale or end-of-support date for VPOP and described the migration strategy for existing VPOP customers as still being planned.

    BRKCCT-2723 (Cisco Live session deck; exact session title not extractable from the file) · session BRKCCT-2723, VPOP transition slides · Checked 2026-09-22
58. 58
    The live Webex Contact Center administrator release-note article, covering February 2026 through September 2026, contains no entry about vPOP, Common Edge, cloud connected PSTN or Webex Calling PSTN.

    What's new for administrators in Webex Contact Center · full month-by-month entry list as rendered on 2026-09-22 · Checked 2026-09-22
59. 59
    All new Webex Contact Center subscriptions include Webex Calling PSTN services added automatically to the order, and a tenant provisioned before October 2024 may need its partner to add the Webex Calling PSTN service in order to use Common Edge services.

    Set up voice channels for Webex Contact Center · section "Connect to Webex Contact Center with Webex Cloud Common Edge services" · Checked 2026-09-22

Documents

Cite this page

WarmTransfer. (2026, September 22). Telephony during a UCCX to Webex Contact Center migration. WarmTransfer. https://warmtransfer.net/knowledge/uccx-to-webex-cc-telephony-coexistence

@misc{warmtransfer-uccx-to-webex-cc-telephony-coexistence,
  title  = {Telephony during a UCCX to Webex Contact Center migration},
  author = {{WarmTransfer}},
  year   = {2026},
  url    = {https://warmtransfer.net/knowledge/uccx-to-webex-cc-telephony-coexistence},
  note   = {Verified 2026-09-22}
}