Scenario 1: an external call comes in, the receptionist tries to forward it to an external cell phone number, the cell rings but no audio
Scenario 2: an external call comes in, rings on an extension that has follow-me configured with a cell phone number, the cell phone rings and audio is fine.
I’ve tried to add the following settings in the Chan SIP settings (found a few threads on the subject) but no luck:
progressinband=yes
prematuremedia=no
Also added rtpkeepalive=1, still not working
Any other clue on what I should try ? I guess that updating the system would probably be a good thing…
One-way audio is almost always a NAT issue, and this doesn’t sound like it’s violates that rule. The wrinkle is that the FMFM part is strange. Do you have /var/log/asterisk/full logs for a failed call that we can look at?
Potentially this might also be a SIP ALG issue. If your router supports SIP ALG (sometimes called SIP Helper) and have a setting to disable it then do that. With more firewalls it causes nothing but problems and they can be very random in nature. I have had problems in the last whereby transfers will not work at all if extensions are behind a SIP ALG enabled firewall (using a remote PBX), but everything else works OK.