SIPAddHeader Questions

I am in the process of doing an Interop test with FreePBX 2.11/Asterisk 1.8 with our VOIP platform and everything is testing fine except for one feature. We are challenging each outbound call for authentication, which is working fine when the DIDs being used are part of the SIP Trunk I have Asterisk registered to. The issue I’m running into is allowing non-native (other carrier) DIDs to be presented as the Outbound Caller ID number.

The system is using that non-native number to authenticate against which is going to fail. In order for a non-native DID to be passed properly we are requiring the fields “trunk-group” or “tgrp” and “trunk-context”. The trunk-group/tgrp should be the pilot number (username) and the trunk-context should be our SIP domain.

I haven’t really worked with Asterisk is years so I’m very rusty and out of touch with what the new version can do. I’m trying to modify the extensions_custom.conf file with this:

exten => _1NXXNXXXXXX,1,SIPAddHeader(trunk-group: 5555551212)
exten => _1NXXNXXXXXX,2,SIPAddHeader(trunk-context:

I know the issue is me and my lack of knowledge on this so any help would be appreciated on how I can pass those fields and their values in the SIP INVITES for outbound calls. I’m pretty sure that context is wrong or I’m missing something.