00 · Header

DI + Webex Calling Coexistence

T5 · Dedicated Instance

Dedicated Instance and multi-tenant Webex Calling can share one Control Hub org. Calls between them use certificate-based trunks Cisco already built. You activate those trunks. You do not edit them. A user is on one call control, not both.

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01 · Executive summary

Five lines, then why it matters

• If you need calls between the platforms, fold the preconfigured elements into both dial plans. [cite:1]
• Configure a PSTN connection on the default WXC-DI location before the main number. Until that number exists, users cannot make or receive calls through that route group. [cite:1] [cite:2]
• On multi-tenant, new route lists and dial plans must select the route group tied to the certificate-based trunk. [cite:1]
• One local gateway can hold two trunks. The deployment-model article still recommends a site be entirely on one platform, so a given gateway usually has one of those trunks. [cite:3]
• Directory synchronization into Dedicated Instance Unified CM from Control Hub works only when SSO is enabled. [cite:3]

02 · Architecture map

Two call controls, one backbone trunk

flowchart LR
  DI[Dedicated Instance UCM] --- BB[Webex backbone]
  BB --- MT[Multi-tenant Calling]

03 · Core concepts

What Cisco prebuilds, and what you still must do

Names you will see

Where a user should live

Codecs, with the date attached

04 · Ecosystem & sister technologies

Glossary, map, sisters, edges

Glossary

Interop trunk

The certificate-based SIP trunk Cisco creates between Dedicated Instance and multi-tenant Webex Calling over the Webex backbone. [cite:1]

WXC-DI location

The default multi-tenant location. It needs a PSTN connection and a main number before calls use its route group. [cite:2]

ECBN

Emergency callback number on that location. When set, an emergency call presents it to the PSTN provider. [cite:1]

X-DI-WxC-otg

SIP header the normalization script adds toward Webex Calling. [cite:2]

Group filter

Limits Dedicated Instance Unified CM directory sync to users designated for Dedicated Instance. [cite:3]

CCP for both

The deployment-model article says both multi-tenant and Dedicated Instance users can use existing Cloud Connect PSTN partner peering to the multi-tenant platform. [cite:3]

Mind map

mindmap
  root((DI plus multi-tenant))
    Trunks
    Numbers
    SSO
    WxCC
    PSTN

Sister-technology matrix

Integration map

Cross-platform bridges

Future-integration hooks

• Canon plan: T5-R02 keeps the two Dedicated Instance connections. ny65x1bb also says Edge Connect 3.0 can carry multi-tenant, Dedicated Instance, and Meetings on one peering path. Quote both articles. Do not delete either sentence. [cite:3]
• Canon plan: T5-R06 is the move onto Dedicated Instance. This room is the steady state after some users stay multi-tenant.
• Interop and base-configuration headers are older than 12 months. re-check prefixes and the codec list before a cut. [cite:1] [cite:2]

Ecosystem troubleshooting

05 · Flow

From activation to a cross-platform call

06 · Config

Activate the trunk without renaming it

1. Sign in at admin.webex.com. Open Management → Locations. Select the default location prefixed WXC-DI. Open Calling, then Manage in the calling connection. [cite:1]
2. On connection type, select the default route group prefixed WXC-DI, check the disclaimer, and continue. Add the main number now or accept that calls wait. [cite:1]
3. On the same location, set Callback Number under Emergency Calling and save. [cite:1]
4. Under Services → Calling → Call Routing, confirm certificate-based trunks in the trunk-type column. Create the route list and the dial plan with that route group as the routing choice. [cite:1]
5. On Dedicated Instance, point the xWxC route list at the xWxC_MT route group. Move any route pattern that still targets a registration trunk. [cite:1]
6. Leave the default trunks in place. Update the RedSky account ID. Do not invent a new interop trunk name. [cite:2]
7. Assign each user to one calling service. Keep contiguous numbers and group features together. [cite:3]
8. If agents are on Dedicated Instance for Webex Contact Center, copy Factory Default Lossy, order G.711 U-law, G.711 A-law, OPUS, and apply that list on the regions the integration article names. Do not do that reorder for a non-WxCC trunk just because the interop article lists the same three codecs. [cite:4] [cite:1]

Interop card (ofrt6u / 2vpf1 / ny65x1bb). No customer secrets.
  MT prefix:           WXC-DI
  UCM prefix:          xWxC
  trunks:              one per DI data center, do not modify or delete
  before calls:        PSTN connection, then E.164 main number
  old registration:    repoint route list to xWxC_MT route group
  header:              X-DI-WxC-otg
  script spelling:     xWxC_MT_Normilization
  user assignment:     DI or multi-tenant, not both
  group features:      pickup, hunt, manager/secretary on one platform
  DI-directed codecs:  G.711U, G.711A, OPUS (header 2024-09-03, re-check)

07 · Limits

What is quantified

08 · Troubleshooting

Ten coexistence failures

09 · Self-question ladder

Twelve rungs

10 · Lab

A paper lab. Do not delete a production interop trunk.

• Goal: read a mixed-estate dial plan and mark what Cisco prebuilt versus what you must add.
• Prereq: ofrt6u, 2vpf1, and ny65x1bb. No org you do not own.
• Step 1. List objects prefixed WXC-DI and xWxC. Expected: you can explain both prefixes.
• Step 2. Find the main number on the default location. Expected: calls are blocked without it.
• Step 3. Find any registration trunk still used by a route pattern. Expected: it moves to the certificate route group.
• Step 4. Pick ten users and say which platform each is on. Expected: none are on both, and no hunt group is split.
• Evidence: the route-group name the dial plan uses, and whether SSO is a prerequisite for sync.
• Break it: delete WXC-DI-TRK to “clean up.” Recovery: you do not. The article says not to delete it.
• Reflection: which codec sentence is the interop article, and which one is only for WxCC.

11 · Quiz

Twelve questions

12 · Audio

Slots for Studio

13 · Interview

Oral answers

30 seconds. Dedicated Instance and multi-tenant Webex Calling interoperate with certificate trunks Cisco creates over the Webex backbone. Multi-tenant names start with WXC-DI. Unified CM names start with xWxC. You add a PSTN connection and a main number, and you point your dial plan at the certificate route group. You do not rename those trunks.

2 minutes. Older registration trunks have to be unhooked. The route list example points at the multi-tenant route group Cisco built for the certificate trunk. A user is on one calling service. Contiguous numbers stay together. Pickup, hunt, and manager/secretary stay on one platform because the features are not fully harmonized. A gateway can trunk to both, and the article still wants a site on one platform. Directory sync onto the dedicated Unified CM needs SSO. A group filter keeps multi-tenant users off that cluster.

30 seconds, codecs. The interop article allows G.711 U-law, G.711 A-law, and OPUS for calls directed through Dedicated Instance. The contact-center article wants that order, U-law first, and only when agents are on Dedicated Instance for Webex Contact Center. Both pages are older than a year. Re-read them.

2 minutes, meetings and PSTN. Cloud Connect PSTN on the multi-tenant peering can serve both populations in the deployment story. If you are not using that, the interop location can be premise PSTN. Meeting call-me in that story comes through Cisco’s internal trunk to Dedicated Instance. The normalization script adds X-DI-WxC-otg so Calling knows which cluster it is. You still type the RedSky account ID yourself.

What you will not say. You will not say a user can subscribe to both calling services. You will not delete WXC-DI-TRK. You will not treat the Edge Connect 3.0 “one peering path” sentence as permission to ignore the two Dedicated Instance connections in T5-R02.

14 · Citations

1. Activate inter-op SIP trunk to Webex Calling multi-tenant — help.webex — article ofrt6u — help.webex.com article ofrt6u — header September 03, 2024, retrieved 2026-10-14. re-check Certificate trunks over the Webex backbone. Prefixes WXC-DI and xWxC. Do not modify or delete the elements. PSTN connection and main number. Repoint to the certificate route group. Codecs G.711 U-law, G.711 A-law, and OPUS.
2. Dedicated Instance for Webex Calling - base configuration — help.webex — article 2vpf1 — help.webex.com article 2vpf1 — header May 27, 2025, retrieved 2026-10-14. re-check Location, trunk per data center, route group. Do not modify or delete default trunks. Script name xWxC_MT_Normilization. Header X-DI-WxC-otg. RedSky account ID is a customer or partner edit.
3. Dedicated Instance – customer deployment models — help.webex — article ny65x1bb — help.webex.com article ny65x1bb — retrieved 2026-10-14. The retrieved markdown did not print a header date. Contiguous numbers. Features not fully harmonized. One calling service per user. SSO required for that directory sync. One platform per site is the recommendation. Edge Connect 3.0 can carry several services on one peering path.
4. Webex Dedicated Instance Contact Center integration — help.webex — article nmhk7ve — help.webex.com article nmhk7ve — header June 27, 2025, retrieved 2026-10-14. re-check Certificate trunks, not registration trunks, for Dedicated Instance to Webex Contact Center. Two agent-phone options. Codec order G.711 U-law, G.711 A-law, OPUS, only for the WxCC integration.
5. How to raise a service request — help.webex — article nvfve88 — help.webex.com article nvfve88 — retrieved 2026-10-14. A DI–MT inter-op SIP trunks request changes the location in the selected region on multi-tenant for the default trunks Cisco created.

15 · Re-engineer later

• Open questions: ny65x1bb header date. Whether the September 03, 2024 codec sentence is still the interop list.
• Facts still marked re-check: ofrt6u, 2vpf1, and nmhk7ve, because those headers are older than 12 months on 2026-10-14.
• Assets missing: location screenshot, trunk SVG export, audio.
• Ideas for v1.0: a prefix card that refuses to print a trunk name Cisco did not print. The articles use placeholders inside WXC-DI and xWxC. Do not fill those placeholders from memory.
• Next review: re-check the three codec sentences and the “do not delete” trunk row.