Being new to the VoIP space (but with plenty of experience with i.e. web and email servers) I tried to get a running system by installing the kamailio package and starting up, trying to get it to behave by looking at log output. I use the blink SIP client in OSX, that has a SIP data dump log view and from that I can deduce that the server returns "SIP/2.0 483 Too Many Hops", however there is nothing helpful in the server logs.
If I set debug=2 i get nothing useful, and if I set debug=3 I get insane amounts of logging, thousands of lines per connection attempt. Finding something meaningful in there seems like a herculean task.
/noa
ps. The actual problem with 483 Too Many Hops sounded a lot like 'Mail loops back to myself' that you get on smtp servers when the relevant virtual domain is not configured, so it seems I was able to handle that problem by adding WITH_MULTIDOMAIN and configuring my domain with kamctl domain add. Now I get "482 Loop Detected" instead, which seems like a non-fatal condition. The logging question still stands though.