Troubleshoot siptrunk


i’m using freepbx on ubuntu 10.04 LTS (with asterisk 1.8.4…1) and I have some troubles for establishing SIP TRUNK to SIP provider.

From the panel it says it is connected.
anyway I cannot give or receive any call with external (internal call runs fine).
On the phone I get the following error : “server unreachable”

Asterisk logfile are empty.
Freepbx logfile doesn’t say much on any existing problem.

I know that my sip provider needed to add some exception to deal with my public IP adress (my provider is also an internet provider and by default only allows devices on its network to connect to its SIP services).

I’m also new with freepbx so I dont want to tell my provider that there is a problem on his side without being sure…

I would like to know how I can troubleshoot the siptrunk connection.
What test to do, what conclusion to make with the results
Is there some logfile that can help ?
Maybe my log doesn’t work well

Tkx 4 any help