We want to use own SIP trunk. We have domain and credentials for authentication from our provider, but we have problem with settings. Our provider says, vapi does not send registration packet. WE have 3hours meeting with the provider where we tried every possible setting on vapi side or provider side

Vapi does not send SIP registration (REGISTER) packets when connecting to a BYO SIP trunk. Instead, it expects your provider to allow direct SIP trunking using the gateway address and credentials you supply—no registration step is performed. If your provider requires SIP registration, this setup will not work with Vapi as currently designed. Please check if your provider can support direct SIP trunking without registration, as shown in this example:

bash
curl -X POST "https://api.vapi.ai/credential" \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer YOUR_VAPI_PRIVATE_KEY" \
  -d '{
    "provider": "byo-sip-trunk",
    "name": "Your Trunk",
    "gateways": [{ "ip": "your.sip.provider.com" }],
    "outboundAuthenticationPlan": {
      "authUsername": "YOUR_SIP_USERNAME",
      "authPassword": "YOUR_SIP_PASSWORD"
    }
  }'

Sources: - [Vapi SIP Trunking Documentation](https://docs.vapi.ai/advanced/sip/sip-trunk) - [Vapi Zadarma Integration Guide](https://docs.vapi.ai/advanced/sip/zadarma)

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

@defichk @Shubham Bajaj Based on the response from @Vapi Support Bot and based on other feedback from other people, the response is accurate. VAPI doesn't perform a

SIP REGISTER

to remote providers, on in other words, it doesn't implement a full B2BUA scenario. This is why people that are using carriers with username/password combinations in most cases will have outbound calling no problem, but inbound calling won't always work. What I've also seen are situations when VAPI will send out a challenge/reponse based

SIP Auth

workflow, but will not populate the

SIP Contact

header in a unique manner across multiple sessions, causing the remote SIP endpoint to simply drop the calls, as they encounter a signalling violation. To resolve the issue above, @defichk if you would like to experiment, I'll be happy to try and configure your accounts on our SBC gateway, and see if that will resolve your VAPI connectivity issue.

Vapi does not send SIP registration (REGISTER) packets when connecting to a BYO SIP trunk. Instead, it relies on your provider supporting direct SIP trunking using the gateway address and credentials you provide—so no registration step is performed. If your provider requires SIP registration, this setup won't work as Vapi is currently designed. Many users in similar situations find that outbound calls may work, but inbound calls can be problematic, especially if the provider expects registration or unique SIP Contact headers for each session. If your provider can enable direct SIP trunking without registration, that would be the best path forward. Otherwise, some users experiment with intermediary solutions like an SBC gateway to bridge the gap.

We have multiple call ID , you can check: a24a7847-d7d3-440f-af70-abd0fa9cc9cc We were testing multiple ways to connect our SIP

Vapi does not send SIP registration (REGISTER) packets for BYO SIP trunks. Your provider must support direct SIP trunking without registration. To set up your trunk, use the following example:

bash
curl -X POST "https://api.vapi.ai/credential" \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer YOUR_VAPI_PRIVATE_KEY" \
  -d '{
    "provider": "byo-sip-trunk",
    "name": "Your Trunk",
    "gateways": [{ "ip": "your.sip.provider.com" }],
    "outboundAuthenticationPlan": {
      "authUsername": "YOUR_SIP_USERNAME",
      "authPassword": "YOUR_SIP_PASSWORD"
    }
  }'

If your provider requires registration, this setup will not work. Consider using an SBC gateway if direct trunking is not possible. Sources: - [Vapi SIP Trunking Documentation](https://docs.vapi.ai/advanced/sip/sip-trunk) - [Vapi Zadarma Integration Guide](https://docs.vapi.ai/advanced/sip/zadarma)

Hey, it looks like you have deleted your phone number, but when digging into the logs, I found the following information which says your calls were declined with status busy, and I suggest you to check with your telephony for this. Let me know if I can help you further.

🔵 07:55:42:681 Received Phone Number Call Status Update: {
  "call_sid": "a51b9xxxe31fa",
  "direction": "outbound",
  "from": "+420xxx91",
  "to": "+4207xxx9xx84",
  "call_id": "d5d8b821-b0bb-123e-d695-02094b04633f",
  "sip_status": 603,
  "sip_reason": "Decline",
  "call_status": "busy",
  "account_sid": "b037xxxxc0281479",
  "trace_id": "",
  "fs_sip_address": "1x60",xxx
  "api_base_url": "httpxxxxi/v1"
}