Troubleshoot No-way Audio Issue with Hairpin Calls on CUBE

Publisher

Cisco Systems, Inc. (www.cisco.com)

URL

https://www.cisco.com/c/en/us/support/docs/unified-communications/unified-border-element/214622-troubleshoot-no-audio-issues-with-hairpi.html

Published

2023-07-18

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

• Technote 214622 says media anti-trombone only fixes hairpin no-way audio if both CUBE and the ITSP support the anti-trombone feature. in context
• Technote 214622 lists a fourth remedy: CUBE sends locally generated STUN packets to the negotiated media address, which can open the far-end firewall. It is configured at dial-peer level. in context
• In a hairpin call through CUBE, neither the caller nor the called party sends RTP until it receives RTP from something in the call path. Cisco calls this a deadlock, and the result is no-way audio. in context
• Technote 214622 warns that with media flow-around, RTP bypasses CUBE, so CUBE cannot terminate media on those calls. in context
• Technote 214622 documents four remedies for no-way audio on hairpin calls through CUBE: a software MTP, media flow-around, media anti-trombone, and having CUBE send STUN packets. in context
• Technote 214622 notes that if media flow-around is configured globally, a media flow-through setting on a dial-peer has no effect. in context
• Technote 214622 attributes the hairpin deadlock to ITSPs that ignore the SDP media address because of firewall restrictions and wait to receive RTP first. That leaves CUBE needing to send RTP first. in context
• The software MTP remedy only works for G.711 calls, because a software MTP can only bridge G.711. Hardware MTPs cannot send the dummy RTP stream. in context
• Technote 214622 calls a software MTP the preferred remedy for hairpin no-way audio, because the software MTP sends dummy RTP packets to both parties and breaks the deadlock. in context
• Cisco gives 4 remedies for hairpin no-way audio on Cisco Unified Border Element: a software media termination point, media flow-around, media anti-trombone, and enabling the border element to send STUN packets to the negotiated media IP address and port. in context
• Cisco describes a no-way audio failure specific to hairpin calls, where a call arriving from an internet telephony service provider is forwarded or transferred back to that provider: some providers disregard the IP address and port in the SDP because of their firewall implementation and transmit only to the source address of RTP they have already received, and on a hairpin call neither end sends first because the IP phone that would normally send dummy RTP after opening its ports is not in the path. in context
• On a CUBE hairpin call to such an ITSP neither party sends media until it receives some, so the call has no audio in either direction and 'show call active voice brief' shows 0/0 Rx/Tx on all legs. in context
• Cisco lists a software MTP that sends dummy RTP, media flow-around, media anti-trombone and locally generated STUN packets as remedies for no-way audio on CUBE hairpin calls, with the software MTP preferred. in context
• Cisco documents that some ITSPs ignore the IP address and port in SDP because of their firewall design and send media only back to the source of RTP they first receive from the far end. in context
• On CUBE hairpin calls, no audio can result from a deadlock where both ends wait for incoming RTP before sending. Documented fixes include software MTP, media flow-around, media anti-trombone and STUN packets. in context
• On CUBE, show voip rtp connections and show call active voice brief are used to check whether RTP streams are set up for an active call when troubleshooting missing audio. in context

Cite this source record

APA

WarmTransfer. (2023, July 18). Troubleshoot No-way Audio Issue with Hairpin Calls on CUBE. WarmTransfer. https://warmtransfer.net/knowledge/sources/cisco-technote-214622-cube-hairpin-no-audio

BibTeX

@misc{warmtransfer-cisco-technote-214622-cube-hairpin-no-audio,
  title  = {Troubleshoot No-way Audio Issue with Hairpin Calls on CUBE},
  author = {{WarmTransfer}},
  year   = {2023},
  url    = {https://warmtransfer.net/knowledge/sources/cisco-technote-214622-cube-hairpin-no-audio},
  note   = {Cisco Systems, Inc. (www.cisco.com), accessed 2026-09-16}
}