On the 'Edit IAX Trunk' page the 'PEER Details' and 'USER Details' sections do not respect the order of directives entered. After a 'Submit' the order presented may be different to that supplied by the user, and is the reverse of the order written to iax_additional.conf. This may not matter for the majority of directives, but for 'permit' and 'deny' it is crucial as the last one to appear takes precedence. Take for example:
deny=0.0.0.0/0.0.0.0
permit=192.168.1.0/255.255.255.0
In this order connections are denied from everywhere except the 192.168.1.x subnet. Reverse the order and all connections are denied. Manual changes to the order in iax_additional.conf confirm this behaviour in asterisk 1.2.19. Both FreePBX 2.2.1 and 2.3beta1 with online updates applied 09 July 2007 consistently put the deny after the permit in iax_additional.conf irrespective of the order entered.