At the moment we are using Asterisk with few ISP SIP Trunks where we are getting the calls. We need that every ISP SIP Trunk to get into a different context. We are authenticating all ISP as a friend by IP Address.
To be able to scale the current infrastructure - we put the SIP Proxy (Kamailio) in front - and forwarding all SIP messages to the Asterisk Farm. But, the problem now is that all SIP Messages are coming from one single IP (kamailio) - and we cannot any more to distinguish between ISP and send calls to the correct context. I was looking on the internet and I found that this could be possible by changing 'From: ’ header and for every SIP Trunk add userfrom field - but in this case, the callerid(num) variable will not be available in asterisk or will be the wrong one. Is there any other methods to solve this issue?