Now that we have reviewed the common pitfalls of NAT, we can go over the various types of NAT situations that you may encounter. Basically you will probably be in a situation where either your phone or PBX is behind NAT talking to a SIP endpoint that is not behind NAT (or vice versa). Even worse, you might end up in the dreaded double-NAT situation where both sides of a connection are independently behind their own individual NAT routers at the same time.
A double-NAT scenario looks like the following diagram:
Let's start with a sane, yet challenging situation where you have a phone at your house that can't understand NAT and you want to register to your FreeSWITCH server that is on the public Internet. The good news is that this situation is already covered for you by the example FreeSWITCH demo configuration. The core of FreeSWITCH...
