I have got block of numbers from ITSP. It starts from 11 11 510 to 11 11 519. I have 5 VOIP channels. Setting up the first line (1111510) was easy. Here is a log of successful inbound call: 02:04:14.453 Call::Terminate [CM503008]: Call(30): Call is terminated 02:04:14.437 LineCfg::getInboundTarget [CM503011]: Inbound out-of-office hours' rule for LN:<secret> forwards to DN:300 02:04:05.093 CallCtrl:nSelectRouteReq [CM503004]: Call(30): Calling: RingAll:300@[Dev:sip:firstname.lastname@example.org:5060] 02:04:05.078 Line:rintEndpointInfo [CM505003]: Provider:[DetelProvider] Device info: Device Not Identified: User Agent not matched; Capabilities:[reinvite, replaces, able-no-sdp, recvonly] UserAgent: [3CXPhoneSystem 5.0.3790.0] Transport: [sip:192.168.2.5:5060] 02:04:05.078 LineCfg::getInboundTarget [CM503011]: Inbound out-of-office hours' rule for LN:<secret> forwards to DN:300 02:04:05.046 CallCtrl:nIncomingCall [CM503001]: Call(30): Incoming call from 0444444@(Ln.<secret>@DetelProvider) to [sip:email@example.com:5060] 02:04:04.796 LineCfg::getInboundTarget [CM503011]: Inbound out-of-office hours' rule for LN:<secret> forwards to DN:300 ****** On the other side, setting up inbound rule for second external number (1111512) is a bit of the problem. Here is a log of unsuccessful inbound call. 02:03:56.890 evt::CheckIfAuthIsRequired::not_handled [CM500002]: Unidentified incoming call. Review INVITE and adjust source identification: INVITE sip:firstname.lastname@example.org:5060;user=phone SIP/2.0 Via: SIP/2.0/UDP 184.108.40.206:5060;rport=5060;branch=z9hG4bK4452a28fa4e271639a2a75e95fa44d10 Max-Forwards: 70 Contact: [sip:220.127.116.11:5060] To: "1111512"[sip:email@example.com:5060] From: "0444444"[sip:firstname.lastname@example.org:5060;user=phone];tag=GR52RWG346-34 Call-ID: 203382008-83FCF35146940203170@18.104.22.168 CSeq: 1 INVITE Allow: ACK, NOTIFY, OPTIONS, REFER, INFO, BYE, CANCEL, INVITE Content-Length: 0 Remote-Party-ID: "0444444" [sip:email@example.com:5060];party=calling;screen=yes;privacy=off 02:03:56.890 evt::CheckIfAuthIsRequired::not_handled [CM302001]: Authorization system can not identify source of: SipReq: INVITE firstname.lastname@example.org:5060 tid=4452a28fa4e271639a2a75e95fa44d10 cseq=INVITE contact=22.214.171.124:5060 / 1 from(wire) where: 126.96.36.199 is external IP of my ITSP 188.8.131.52 is my external IP 192.168.2.xx is my internal IP schema 1111512 is my public tel number 0444444 is public telephone number used to test connection (completely independent to 3CX PBX) <secret> is my ID towards ITSP I can not simply register second line, because 3CX refuses creation of another VOIP account with the same ID. Any ideas how to solve the problem?