First post here, hello people. I just installed 3CX PBX on a server for testing. I registered two VoIP phones fine. The next step was to connect to a LANCOM (I only found one post here concerning the LANCOM and wasn't useful) router that is also a VoIP proxy/gateway and server (PBX) and ISDN/analog gateway/PBX too! It can have VoIP registrations to SIP providers, ISDN connections to landline and on the other side LOCAL VoIP users (like your PBX), ISDN and analog users and "blend" all these I/O transparently. Connecting to this device by means of registering a few 3CX "lines" (VoIP or PSTN) and on the LANCOM, and a few VoIP "provider lines" on 3CX is not the proper way (and will not work properly because it won't be treated as "trunk" on any of the two sides). You see LANCOM has a "SIP PBX" registration also, that is meant exactly for this situation: interconnection between two SIP PBX. In this registration you only have those entries: sip pbx name, sip domain/realm, registrar (optional), outbound proxy (optional), port, default password, call prefix, line prefix and permited codecs. Unfortunately 3CX gives no way for INBOUND registration other than SIP users and cannot "trunk" link properly with a SIP PBX AFAIK. Is there anything for me to try? Is this some extra functionality you might consider adding? --- Also a problem I noticed is that somewhere between changes the local extensions stayed unregistered and I couldn't register them even by restarting 3CX services (am I allowed to do this? is the first service enough?). After some minutes (minutes not seconds) the first registered and then the second. Strange isn't it?