Hi, I do have the 3cx phone system installed here (it is the free version that is going to be updated to paid SBS version soon). I got all extensions working within the network and over our VPN server, two PSTN lines (both controlled by the Linksys SPA 3102 gatweay), everything works great. Now I set my test Linksys SPA901 IP phone to register from my home network through my firewall onto the 3cx phone system within our company network. It registers flawlessly, but when I try to make a call from my 3cx VoIP client (nr. 106, connected over VPN) to that IP phone (nr. 107, no VPN), it is not successful. My client says it is ringing, but the IP phone remains silent. After a minute or so the client switches to "busy" tone and this is what I get on the 3cx server: 01:29:47.821 Call::Terminate [CM503008]: Call(9): Call is terminated 01:29:47.790 Call::RouteFailed [CM503014]: Call(9): Attempt to reach [sip:email@example.com:5060] failed. Reason: No Answer 01:29:47.758 CallLeg:nFailure [CM503003]: Call(9): Call to sip:firstname.lastname@example.org has failed; Cause: 408 Request Timeout; internal 01:29:47.431 CallLeg:nFailure [CM503003]: Call(9): Call to sip:email@example.com:5060 has failed; Cause: 408 Request Timeout; internal 01:29:14.961 CallCtrl:nSelectRouteReq [CM503004]: Call(9): Calling: Shared:107@[Dev:sip:firstname.lastname@example.org:5060, Dev:sip:email@example.com:5060] 01:29:14.930 CallCtrl:nIncomingCall [CM503001]: Call(9): Incoming call from Ext.106 to [sip:firstname.lastname@example.org:5060] Watching the line status monitor I found that during this time the status "LED" of my client changed to amber (calling), while status of the IP phone remained green (idle). On the contrary, trying to make a call back to my client, the IP phone worked perfectly, including audio. The IP phone as well as my client status "LED" changed both to amber and connection was established. So the result is that I cannot make calls to the IP phone as it is, but I can call from the IP phone the rest of the internal 3cx numbers. When I set the phone into our company network, reconfigured it and did try to call it, it ringed. I have set all necessary ports on the company firewall (5090, 5060, 9000 - 9015, 3478). The firewall test on the 3cx server did go well. I also opened and transferred the port 5060 on my home firewall to the IP phone. I was guessing for a while that my ISP might block the SIP ports, but in that case I would have not at all made a call from the IP phone. This must be some matter with either the company firewall, or the home firewall - perhaps some routing mishap? I have no idea as to how to debug this strange behaviour. Company firewall is Linksys RV042, my home firewall is Linksys RVS4000, IP phone is Linksys SPA901, there is the latest version of the 3cx server installed on the server. All devices were upgraded with latest firmware. I will be grateful for any hint or advice that would help me to solve this issue.