extension.conf
[local]
exten => 1004,1,Dial(IAX2/IT@192.168.100.52)
exten => 1006,1,Dial(IAX2/trn@192.168.100.12)
exten => 1007,1,Dial(IAX2/trn1@192.168.100.242)

sip.conf
[IT]
type=friend
host=dynamic
context=local
accountcode=IT
username=IT

iax.conf
[general]
bindport = 4569           ; Port to bind to (IAX is 4569)
bindaddr = 192.168.100.197    ; Address to bind to (all addresses on machine)
disallow=all
allow=ulaw
allow=alaw
allow=gsm
mailboxdetail=yes

#include iax_additional.conf
#include iax_custom.conf
#include additional_a2billing_sip.conf


[IT]
type=friend
host=dynamic
context=local
accountcode=IT
username=IT