UC LabFree University

T3 · T3-R02

CUBE as a B2BUA

ExportSVGPNGHTMLSheet

Learn it in 5 minutes

  • CUBE terminates one dialog and starts another.
  • Codec, DTMF, and header policies are per leg unless you bind them.
  • Media can anchor on CUBE or flow around it, depending on the design.
  • A 200 on the CUCM leg does not prove the carrier leg is up.
  • Read IP addresses on each SDP.
ExportSVGPNGHTMLSheet

Visual

CUBE as a B2BUA diagram
ExportSVGPNGHTMLSheet

What is going on

Unified Border Element is Cisco's SBC on IOS. Treat it as two calls. Mid-call services such as transfer and hold are re-INVITEs CUBE must map. If you only capture the CUCM side, you will miss a carrier rejection.

Confirm before relying. DSP and license names vary by platform. Confirm before you order hardware.

ExportSVGPNGHTMLSheet

Worked example

CUCM sends G.711. The carrier peer allows G.729 only. CUBE can transcode if a DSP is configured and licensed for that feature. If not, the carrier leg fails and CUCM may see a different cause than 'no DSP'.

ExportSVGPNGHTMLSheet

Quiz

1. CUBE forwards one SIP dialog unchanged, like a proxy.

ExportSVGPNGHTMLSheet

Ecosystem

Sister pieces sit on the ecosystem page: the glossary, the mind map, the integration map, and the sibling labs.

  • B2BUA — A user agent that sits between two dialogs.
  • Media anchor — RTP terminates on the SBC.

Config. Show the inbound peer, the outbound peer, and whether a transcoder profile is bound.

Troubleshooting. Capture both legs. One ladder is not the call.

Bridge. The same CUBE can be a Webex Calling local gateway and a CUCM PSTN gateway. Those are different dial peers.

Mind map, sister technologies, and future hooks live on the ecosystem page.

ExportSVGPNGHTMLSheet

Sources

Product screens move. Confirm the guide for your release before you change a live system.

ExportSVGPNGHTMLSheet

Sources and go deeper

Opened 2026-10. A row marked confirm has no link, because that page was not verified.

sources.json Markdown