Twilio SIP Trunking with CUBE

[Theofilos Tzachristas]

Hello all,

I am working on a lab setup using Twilio SIP trunk, Cisco 2821 with IOS: c2800nm-ipvoicek9-mz.151-4.M3.bin, and CUCM (System version: 9.1.2.11900-12).

I am trying to test incoming calls. The call is successfully sent to CUCM, I can hear the ringing tone, but when the call is answered, it gets disconnected (Picture attached)

I have also attached the

debug ccsip messages

and

debug ccsip all

output.

[Theofilos Tzachristas · Accepted solution]

The problem occurred, because the CUBE was sitting behind a NAT firewall

https://www.twilio.com/docs/sip-trunking/troubleshooting#problem30

Changing the SIP headers fixed the issue.