Just saw that voip.ms does support the IAX2 protocol and went to test it out. I have it working with an IAX2 trunk and an Chan SIP Extension. Is this backwards? My cisco phones are SIP only. Is there any benefit running an IAX2 trunk with a Sip extension?
One of the things that helps my customers with questions like this is that you should think of Asterisk as “the phone”. It answers calls coming in from your external trunks and then (acting as an agent) forwards that call to a destination in the network.
So, if you follow the logic of that - the calls come in from someplace on a trunk, using a protocol. Asterisk (which is managed by FreePBX) understands. It looks in it’s config file and says “Oh look, a phone is available” and sends the call there. It serves as a translator for the call (since it’s actually talking to the trunk) and you’re all set.
This means that you have to stop thinking of the thing on the desk as a “phone” - it doesn’t have a line to the outside world. It knows nothing of the big, bad, ATM network. It talks to Asterisk and asks it nicely to do things for it.