Hi all. I'm still not getting proper behavior from 3CXPhone sometimes. Some inbound calls keep ringing forever without timeout, while others will complete but have a terrible delay. I still think it's related to my firewall settings so I hope this thread will serve as the definitive list of what ports must be open for 3CXPhone to always work. The environment is: 3CXPhone 5.0.14900.0 in Windows 7 connecting only to SIP providers (no PBX). Under 'General Settings', the RTP port range is 16384-16482 and Local port is 5070 with the Any box unchecked. Right now, my DD-WRT router is forwarding the following inbound ports for VoIP to my desktop computer (192.168.1.13): UDP 5060-5080 to .13 UDP 16384-16482 to .13 UDP 3478 to .13 (STUN?) Are there any other ports I should add or remove? Please assume, as with most consumer routers, that there are no restrictions on outbound ports (source or destination). Thanks for your input and to 3CX for this free softphone (that I wish worked perfectly for me).