Anton Aylward wrote:

Just to make my point: I'm being (currently) a Netgear NA/firewall. this is a (low cost) Cisco LinkSys ATA.

I think I've got one of those too - SPA2102? Hmm no, the interface isn't quite the same.

As you can see in this snapshot, there's no STUN configured, but I get incoming (though for some reason most come when I'm not at home and go to VM and remarkably few actually DO leave a message, which says something about attitudes these days and makes me wonder why people use the phone at all) and have no problem with outgoing :-)

My service provider told me quite explicitly NOT to use STUN. Looking at the various HOW-TO on their wiki for other devices, NONE, absolutely NONE of them, be they VoIP enabled smartphones, softphones like Zoiper, various other ATAs from a variety of vendors, need to have STUN configured. Yes mention of NAT comes up and when it does, again, quite explicitly STUN is to be "blank".

And you're absolutely 100% positive these devices are behind a NAT router? Then they must have keep-alive enabled. Anoton, your NAT router maintains a map/table of connections - internal addresses, external addresses and port numbers. Unused connections are flushed after a while. Unless the device uses STUN or keep-alive, that table will not maintain the needed information to know where to direct an incoming call. Maybe check your config for "NAT Keep Alive". The screenshot is from my SPA2102 which connects directly to asterisk. /Per