When setting up a new SIP trunk with a provider or troubleshooting call failures it is important to be able to capture a signaling trace of an outbound call. This is also important when troubleshooting SIP registration issues with a new provider.
In Asterisk for example, turn on SIP debugging via the Asterisk CLI using the sip set debug commands.
Sip set debug peer on – turns on SIP debugging globally showing all SIP traffic to and from the Asterisk gateway.
Sip set debug IP xxx.xxx.xxx.xxx – debug only message to and from a particular IP address.
Sip set debug off – Turns off all SIP debugging.
Please be familiar with how to turn on debugging.
If enabling debugging on the switch is not preferred, use a network protocol analyzer such as Wireshark to capture the SIP and media traffic on the calls. To learn more about Wireshark, please visit http://www.wireshark.org/ This site includes step by step videos on how to setup Wireshark on a network.