VoIP newbie seeks advice!

Archived from groups: comp.dcom.voice-over-ip (More info?)

Hello,



I've just bought a Sipura SPA 3000 after having a play around with XLite and
being quite happy with VoIP (using 1899.com).



However, when I make a call over VoIP, the person I'm calling can hear me,
but I can't hear them.



From looking around the web, it sounds like this is a common problem when a
hardware VoIP device is behind an NAT (as mine is). However, I haven't
really found a solution in works of one syllable! (I really am very new at
this whole VoIP thing).



My internet connection is via a cable modem (2Mb down, 512Kb up), and the
cable modem is plugged into a Linksys BEFSR41 router. My SPA 3000 is
plugged into one of the ports on this router.



I've heard that a STUN server should be able to get around NAT problems, but
although I've set a STUN server in the SPA config, I still get the same
problem.



My router supports uPnP, which, again, I understand should make things
easier! (I also know very little about uPnP I'm afraid!).



I get the same problem with a couple of different SIPs I've tried.



Does anyone have any ideas? Am I correct in thinking it's a NAT problem?
Is it worth me putting the SPA in the DMZ and see if that works? Otherwise,
do I need to forward any ports to the SPA? (although I thought STUN and/or
uPnP got around this problem!).



Help!



A.