Stun for SIP (VoIP)

[striky]

I have just recently set up pfSense in my home network, but I am experiencing some problems getting voip to work.
I have a Tecom GW1000 ST voip adapter that, according to my Internet provider, uses STUN for SIP. The box is not reachable by IP.
I have the Tecom adapter connected to the LAN-interface of pfSense (via a switch), as all of my computers.
My problem is that it is not possible to make incoming calls, and outgoing calls are only "one way" (I don't hear what the other part is saying). Clearly, this is related to STUN for SIP not working, and that the firewall is blocking incoming calls and incoming speech.

How do I solve this? I guess adding another NIC and putting the voip adapter in a DMZ (with all ports open) would work (?), but maybe there is some way of getting STUN for SIP working?

[Cry Havok]

Have a look here.