Sorry to interrupt.
If you are registering a device behind your * with a simple masquerade and you are still dropping calls after 30 sec, there is something wrong with your config. This should take 30 seconds to setup like he said.
set up a no frills network, one external IP, one private subnet with srcnat masquerade. Make sure connection tracking is on. You do not have to do ANYTHING ELSE. I have over a hundred extensions/DID's set up just like this.
If you have a * server behind your MT.....
Did you think of looking at your sip.conf
[
general]
localnet=192.168.0.0/255.255.0.0 ; or your subnet
externip=x.x.x.x ; use your address
[YOURREMOTEPEER] ; your peer's name
nat=yes
qualify=yes ; Force keepalives
in rtp.conf
rtpstart=20000
rtpend=25000
This may help quite a bid for registering outside devices to your src nat'd network.
Also I x-lite has an option to register every x seconds, drop that below 30.
Finally on your mt, set up a no frills network, one external IP, one private subnet with srcnat masquerade, and forward port 5060,5061 and 20000-25000 to your with a dst nat on the external port only (so as to not create a loop). Make sure connection tracking is on.
THIS WORKS AND IS EASY