Hi New here! I've tinkered with Asterisk in the past but never gone the whole hog, this time I'm trying to go all in. I've got IncrediblePBX 13 running on a CentOS 6.9 guest on my FreeNAS box. I've managed to create a couple of trunks, routes and extensions. I've got my landline coming in by connecting to my FritzBox 7490 as a trunk, which is great. But I'd like to use the handsets connected to the FritzBox as extensions. As far as I can tell, and according to https://www.luxgruppe.de/tech/?p=261 (which I only found thanks to this forum) it should be as straightforward as creating SIP extensions in Incredible PBX and then adding them as "Telephone Numbers" in FritzBox. Except I can't seem to get it to work. Here's my settings on the Fritz!Box. I'm just trying using the default extension on Incredible at the moment. Telephone provider: Other Telephone Number for Registration: 701 (extension in asterisk) Internal Telephone Number in the FRITZ!Box: 701 (not sure I understand this field tbh) Username: 701 Password: **** Registrar: 192.168.178.55 It doesn't connect and the Fritz event log says "Registration of Internet telephone number 701 failed. Reason for error: Remote site not responding. Timeout." There's nothing obvious in the asterisk logs, it's almost as if the connection is being rejected by the firewall on IncrediblePBX. I can connect to the same extension using a softphone, so it's allowed to access within the network. I can see that other people have gotten this to work, so I must just be missing something. Does anyone have any hints?