I am having trouble getting VAPI to register to an external SIP (I have tried freeswitch from AWS and it connects correctly, I get the call). When I set it up in VAPI a voice tells me that it is not possible to communicate with the phone. VAPI has registered correctly to the SIP, but i dont receive calls . how can I get a log of these failures? I have checked api logs but nothing. Any idea what could be going wrong? https://cdn.discordapp.com/attachments/1398625948932378674/1398625949481959516/Captura_de_pantalla_2025-07-23_a_las_5.34.11_p._m..png?ex=68860b6b&is=6884b9eb&hm=f4bc6b2f722a1afdc4513f5596811fc6b5d4781ef40d8f7665f43d2f49735509& https://cdn.discordapp.com/attachments/1398625948932378674/1398625950220030023/Captura_de_pantalla_2025-07-23_a_las_5.34.52_p._m..png?ex=68860b6b&is=6884b9eb&hm=5a147671dac465a3958f3f722ce545423903cbf6b9442016447a3868eeea1914&

Vapi doesn’t actually register with SIP like a softphone. It expects your SIP provider to allow direct trunking without REGISTER and send INVITEs straight to Vapi. Check if your SIP provider supports direct SIP trunking (no REGISTER needed). Whitelist Vapi IPs (44.229.228.186 + 44.238.177.138). Make sure your provider routes calls to the correct SIP URI (e.g. sip:xyz@sip.vapi.ai). If still failing, ask your provider for PCAP/logs to see if INVITEs even reach Vapi.

This is the response of my switchboard technicians: At the meeting it was commented that the external system was going to register in the same way as an extension. In this sense we do not have to authorize their IPs, in the same way that we do not authorize the IPs of the extensions when they try to register from a different location (teleworking or change of location). We see that extension 3500 is indeed registered.

Vapi doesn’t use SIP REGISTER like softphones, it requires your SIP provider to support direct trunking and send INVITEs directly to sip:xyz@sip.vapi.ai. Ensure your provider allows this, whitelist Vapi’s IPs (44.229.228.186, 44.238.177.138).. https://vapi.ai/community/m/1375113468457386114

Hi Kings big, thnks for your reply, I have already done those steps for BYO SIP Trunk - VAPI, and the PBX tells me that it is connected to vapi correctly. But when I make a call I get nothing, and it gives failures when making outgoing calls.

Hey! To help track down this issue, could you share: - The call ID This would really help us figure out what went wrong!