Thanks @cynjut for pointing this out. I am slowly gaining some understanding and now am also looking for a way to connect Fritzbox (IP 192.168.1.1) and Asterisk (IP 192.168.1.27) trunk-to-trunk rather than by 1 extension only. This would give the ability to dial arbitrary numbers on each side (Dial(SIP/[email protected]/arbitrary) in extensions.conf - as opposed to hardcode device-with-extension entries in sip.conf), and I want to have conference rooms coming in from the Fritzbox with more than 1 participant.
From FritzBox to Asterisk (F2A), I set up one “9000” “Internetrufnummer”.
For the way back (A2F), I set up a friend sin sip.conf with defaultuser=9000,
i. e. sort of mirrored accounts for the same purpose (establishing a trunk - not just a single channel).
However, F2A I best case see yet another caller ID (624) that cross-triggers somehow and not the external caller’s ID, and A2F the call does not seem to be routed at all (I see nothing in the FritzBox telephony logs - not even for specifying wrong login credentials).
My failed approaches - sip.conf, trunk definition, SIP account for FritzBox:
[trunk-fritz0]
type=friend
username=9000
secret=9000
host=192.168.1.1
fromdomain=fritz.box
[9000]
type=friend
defaultuser=9000
secret=9000
host=dynamic