If I setup 3cx to forward my inbound calls to an IVR, voicemail, or even a direct extension, all the calls drop immediately within 1 to 2 seconds. If the call goes to an extension, the SIP phone recognizes an incoming call for just a few milli-seconds, and never stays connected enough to let a ring tone come through. Dialing outbound is not an issue, nor the internal IVR #, or other extensions, from multiple SIP phones internally (android phone (3cx, sipdroid) + Xlite combinations). I got similar behavior when I tried pfsense with freeswitch for inbound (possibly a configuration issue as well on my end). I am using flowroute as my SIP trunk provider. Below is my log: 20:38:28.703 [MS210001] C:7.2:Answer received. RTP connection[unsecure]: 127.0.0.1:40620(40621) 20:38:28.703 Remote SDP is set for legC:7.2 20:38:28.609 [CM503008]: Call(7): Call is terminated 20:38:28.562 [CM503025]: Call(7): Calling Ext:Ext.8000@[Dev:sip:firstname.lastname@example.org:40600;rinstance=737240aa4ae642ab] 20:38:28.562 [MS210002] C:7.2:Offer provided. Connection(transcoding mode): 127.0.0.1:7020(7021) 20:38:28.546 [CM503004]: Call(7): Route 1: Ext:Ext.8000@[Dev:sip:email@example.com:40600;rinstance=737240aa4ae642ab] 20:38:28.546 [CM503010]: Making route(s) to <sip:firstname.lastname@example.org:5060> 20:38:28.546 [MS210000] C:7.1:Offer received. RTP connection: 220.127.116.11:9860(9861) 20:38:28.546 Remote SDP is set for legC:7.1 20:38:28.546 [CM505003]: Provider:[Generic SIP Trunk -] Device info: Device Not Identified: User Agent not matched; Capabilities:[reinvite, replaces, able-no-sdp, recvonly] UserAgent:  PBX contact: [sip:email@example.com:5060] 20:38:28.515 [CM503001]: Call(7): Incoming call from +15555555555@(Ln.10000@Generic SIP Trunk -) to <sip:firstname.lastname@example.org:5060> 20:38:28.500 [CM503012]: Inbound out-of-office hours rule (unnamed) for 10000 forwards to DN:8000 20:38:28.500 Looking for inbound target: called=+14444444444; caller=+15555555555 20:38:28.500 [CM500002]: Info on incoming INVITE: Key: 8000 = Extension for IVR 33333333 = User Account Name on SIP Registration 4444444444 = DID # 5555555555 = source device's # that dialed the call outbound to DID # 18.104.22.168 = WAN IP 192.168.5.250 = LAN IP Address that C3X is binded to I am forwarding 5060 UDP from my router to this C3x box. Any advice would be very much appreciated!