Configure DTMF Relay on CUBE

Publisher

Cisco Systems

URL

https://www.cisco.com/c/en/us/support/docs/unified-communications/unified-border-element/200412-DTMF-Relay-and-Interworking-on-CUBE.html

Published

2023-05-15

Updated

unknown

Accessed

2026-09-24

HTTP status

200

License

Cisco documentation terms; no-redistribution; short excerpts and locators only

Source notes citing this source

• Cisco's CUBE technote recommends RFC 2833 toward SIP service providers and both RFC 2833 and KPML toward Unified CM or CME. in context
• On CUBE, interworking RFC 2833 with G.711 in-band audio DTMF requires DSP transcoding resources and G.711 end to end; Cisco states the other DTMF interworking cases are handled without a transcoder in flow-through calls. in context
• Cisco's fix for duplicate digits is to configure dtmf-relay rtp-nte digit-drop on the inbound dial-peer and the out-of-band method on the outbound dial-peer, so CUBE suppresses NTE packets and relays only the out-of-band digits. in context
• When CUBE interworks rtp-nte to an out-of-band method without digit-drop, the same digit is sent both in RTP and out-of-band and the far end sees duplicate digits. in context
• On CUBE, DTMF relay is disabled by default on SIP and H.323 dial-peers except SIP INFO, so a relay method has to be configured. in context
• Cisco's CUBE DTMF technote (updated May 2023) states that Unified CM does not support SIP INFO for DTMF. in context
• In-band DTMF is recognised reliably only on G.711 (ulaw or alaw); low-bit-rate codecs distort the tones so they may not be recognised. in context
• Cisco says audible in-band DTMF works reliably only if the call uses G.711 uLaw or aLaw, because compressing codecs distort the tones and can make them unrecognisable to the receiver. in context
• Cisco's CUBE DTMF tech note uses debug voip rtp session named-event to show RFC 2833 digit transmission and debug ccsip messages to show SIP DTMF capability advertisement. in context
• Cisco warns that transcoding a call from a low-bit-rate codec to G.711 most likely distorts in-band DTMF tones as well. in context
• RFC 2833 NTE payload types and attributes are negotiated between the two ends at call setup in the SDP body of the SIP messages. in context
• When both unsolicited NOTIFY and NTE are negotiated on SIP, Cisco IOS chooses unsolicited NOTIFY and suppresses the in-band RFC 2833 NTE packets to avoid double tones. in context

Cite this source record

APA

WarmTransfer. (2023, May 15). Configure DTMF Relay on CUBE. WarmTransfer. https://warmtransfer.net/knowledge/sources/cisco-technote-200412-cube-dtmf-relay

BibTeX

@misc{warmtransfer-cisco-technote-200412-cube-dtmf-relay,
  title  = {Configure DTMF Relay on CUBE},
  author = {{WarmTransfer}},
  year   = {2023},
  url    = {https://warmtransfer.net/knowledge/sources/cisco-technote-200412-cube-dtmf-relay},
  note   = {Cisco Systems, accessed 2026-09-24}
}