Hi, I have a strange problem when calling outside numbers. Situation : Everything worked fine also outside calls. Until I recently moved to another town and got a new modem installed by (Telenet Belgium). This new modem is a modem/router in 1 device. But I wanted to use my old router so I hooked my old router behind the new modem/router and configured DMZ to the new router. I started my server with 3CX and everything connected after I manually set my dyndns ipadress to the new public ip adress, also external extensions connected back to my 3CX PBX. So I was happy everything went fine, I tested internal call it rings and works great ! But when I make an external call to my cell phone or a fixed line phone, I hear no ringing when dialing (totally no sound) !!! My cell phone rings I can pickup the call and audio is 2 way without any problems. Info : I work with a VOIP provider I tested a direct connection with my phone to the voip provider (then everything works fine, I hear ringing when I dial an external number) I tested to connect the 3cx pbx directly to the modem/router but same problem (no ringtone) The modem/router gives ipadresses of 192.168.0.xxx , my router thats behind this modem/router gives ip adresses of 192.168.40.xxx I searched the forum, found some people with the same problem but no clear resolution. The problem must be something that is not rooted wel with this new modem/router, the old modem was only a modem and gave an public ip to my router. Now my router has an 192.168.0.XXX wan ipadress. The firewall test came out with all succes !! I spended a whole day on trying to get this working but can't find a solution.