Hi dicko,
Thank you very much. In the meantime, I checked the issue further, found a solution, but did not understand the cause. Thus, I would very much welcome feedback:
The RTP Port Range in Asterisk SIP Settings and in /etc/asterisk/rtp_additional.conf are always sychronized. This does seem to work as it should.
Our carrier (Deutsche Telekom AG) specifies RTP ports 30000 through 31000 plus inbound port forwarding for UDP packets. In line with recommendations, I did set RTP port ranges of 30000 through 30099 (more than wide enough for me) plus corresponding port forwarding rules. If I recall correctly, port forwarding did make sense one or two years ago. Today, I could not find that to be critical anymore. Furthermore, the carrier also connects if one specifies standard RTP port ranges of 10000 through 20000.
To my surprise, if I take a wireshark trace at my WAN interface, the RTP packets' ports do never correspond to the RTP port ranges set in FreePBX. I have some older traces on file to compare - in the past, there was also no correspondence between RTP port ranges entered and what wireshark finds. Does this make sense??
When upgrading Asterisk SIP Settings from 13.0.14.5 to 13.0.14.6, it changes the RTP port ranges back to 10000 through 20000 regardless of what one did specify before. This did not happen with other recent upgrades which I tested.
In my scenario, I did not immediately notice the change of RTP port ranges due to the Asterisk SIP Settings module upgrade - how should I? When reverting RTP port ranges back to 30000 through 30099 yesterday, I did trigger a FreePBX System Firewall issue. It seems that ony may go either with 10000 through 20000 and the System Firewall on or with other port ranges and the System Firewall off. Unfortunately, this is not obvious - at least this was not obvious to me.
Regards,
Michael