Replying to [p_lindheimer|comment:1]:
> please read the tooltip and corresponding Asterisk documentation if the tooltip is not adequate.
According to Asterisk documentation,
default transport is "transport=udp,tcp", It uses UDP as outgoing, and accept BOTH UDP and TCP.
But now, Freepbx only allows to set "UDP" / "TCP or TLS".
So, if I choose "UDP", then in sip_additional.conf, "transport=udp", therefore, Freepbx will only accept UDP.
If I choose "TCP", then in sip_additional.conf, "transport=tcp", therefore, Freepbx will only accept TCP.
There are no "transport=udp,tcp".
I think Freepbx should allow the following transport options
1. transport=udp only
2. transport=tcp only
3. transport=udp,tcp (it should be a default option)