I’m seeting up FreePBX with SIP trunking from Twilio. It all works except for periodic failures when calling in to the PBX. When this happens I get a recording “all circuits are busy” and the following error is logged:
[2017-09-26 16:25:31] WARNING[C-0000025f] Ext. s: “Rejecting unknown SIP connection from 18.104.22.168”
I don’t know where this IP address is coming from, since it is not listed as one of the IP’s from which Twilio originates calls. A reverse DNS lookup shows that it is registered in Germany. I thought there might be some NAT problem and I tried various NAT settings on my router, but these all made things worse. I suppose I could just create another trunk for this IP address, since the errors always references this exact address, but I’d like to understand what’s happening --??
Thanks much in advance for your advice.