Hi all, I am setting up 3CX and need some help. Problem: there is no audio when calling from one local extension to another local extension - neither can hear the other. There is no problem when calling a mobile phone or another outside phone. 1) I am using remote provisioning of phones 2) I am not using an SBC (I've got this far without it, I can't see the use of it, can anyone enlighten me otherwise?) 3) I have configured the firewall correctly where the 3CX server lives (offsite) and the firewall test passes. 4) I am using V15 under Extensions -> extension -> phone provisioning -> IP Phone, I have selected "direct SIP (STUN - remote)", I have put in the mac address, but the "local sip port of phone" has been auto populated - some of the phones have 5060 and others have 5065. Why are some on 5060 and others on 5065? Should they all be 5060? Or should they all have different ports (no two can be alike)? Also with the "Local RTP Audio Ports Start/Finish" - they are all set to 14000 - 14009, but in the many firewall/NAT tutorials that I have read, they all say that RTP ports to be opened are 9000 - 9500. Can we get a definitive answer here?