Hi, I’m using Asterisk 11.13.1.
I’ve got an issue with Asterisk and Cisco/Linksys phones.
My setup: IP-Phone -> Asterisk -> Mediant2000 -> PSTN
Let’s say that this Cisco SPA504G IP-Phone places a call to a mobile number which is currently switched off. In this case, the carrier sends a voice message in early media “The subscriber’s phone is switched off or out of the coverage…”
Asterisk sends 183 Session Progress with SDP to Cisco SPA504G offering to establish an audio path for the carrier’s message. But then, immediately after that it sends 180 Ringing which confuses Cisco SPA504G and instead of playing the carrier’s message to the caller, it plays local ringing to the caller, which is not acceptable.
Also Linksys SPA922 exhibits the same kind of behavior.
I tested a few softphones and a Fanvil phone and they seemed to not care about the 180 Ringing, but Linksys/Cisco do. Afaik we have like 500 such IP-Phones and it really annoys users to hear generic ringing instead of meaningful messages.
Is there any way to suppress 180 Ringing after 183 with SDP? It doesn’t make much sends to send 180 after 183 at all if the early media path has been established.
Could anybody help with this? I am really struggling to find a solution.