Hey Vapi team, I’m having persistent issues getting inbound calls to work with my custom SIP trunk via Sipgate.de. Here's what I've done and confirmed so far: ✅ Setup SIP Server: sipgate.de Port: 5060 Protocol: UDP SIP ID (Username): 2513697e40 Public IP in Contact Header: ✅ Enabled Options Ping: ✅ Enabled SIP Trunk is fully configured in Vapi and appears to be active. ✅ Tests I can successfully register and receive calls via Zoiper with the exact same SIP credentials. → (Screenshot 1 attached – working inbound call on Zoiper) However, when using Vapi, any call to my number (+4915792320882) results in: "Der gewünschte Gesprächspartner ist zurzeit nicht erreichbar" (The desired contact is currently not available) No INVITE appears in Vapi’s Call Logs (see Screenshot 3) Outbound works fine, and the SIP registration looks healthy (Screenshot 2) ❗ Expected: Vapi should receive the inbound SIP INVITE from Sipgate Agent should be triggered (Benni Boller is assigned) ❌ Actual: Call fails immediately with "not reachable" No sign of INVITE in logs ⏱️ Last test: April 7th, ~18:15 CEST (No Call ID, as no inbound log entry was generated) I'd appreciate any insight you can provide — I'm starting to suspect this might be related to how Sipgate handles public IP routing or missing ACKs from Vapi. Thanks a lot 🙏 https://cdn.discordapp.com/attachments/1358749941010272286/1358749941237026846/Screenshot_2025-04-07_121841.png?ex=67f4f9fe&is=67f3a87e&hm=2cd1620c52b5823bdbe9104218a91e433d2901a5cd65656c1c732047d786bbb0& https://cdn.discordapp.com/attachments/1358749941010272286/1358749941530497055/Screenshot_2025-04-07_122246.png?ex=67f4f9fe&is=67f3a87e&hm=f8271ad55ba97b6aac7e178e527a97b8e945faffe18a8883a26d26235da5d723& https://cdn.discordapp.com/attachments/1358749941010272286/1358749941819768862/Screenshot_2025-04-07_122209.png?ex=67f4f9fe&is=67f3a87e&hm=13694eab6b8e227b6cc116493cb95940e5952dade7648f56cad69353d240d5b3&

Thanks for providing such detailed information about your SIP trunk setup with Sipgate! 👍 I've looked into your issue with inbound calls not working, and I can see this is a complex technical problem that requires specialized expertise. Since you're able to receive calls via Zoiper with the same credentials but not through Vapi, this suggests there might be something specific in how Vapi and Sipgate are interacting. Your suspicions about public IP routing or ACK handling could be on the right track. I've escalated this to our technical team who specializes in SIP trunk integrations and provider-specific configurations. A support engineer will review your case and get back to you with more insights. They'll likely need to investigate how Sipgate's specific implementation works with our system, especially since no INVITE messages are appearing in the logs. In the meantime, could you check if Sipgate has any specific requirements for SIP trunk connections from third-party platforms? This might help our team troubleshoot faster when they reach out.

Message marked as helpful by @H²! 🎉

Hey! I reached out to Sipgate regarding possible third-party SIP trunk requirements. They replied that if your platform requires specific features or behaviors (such as public IP handling, ACK routing, contact header structure etc.), you should send a written request to team@sipgate.de outlining what’s needed. Let me know if you need any additional info from my side or if I should CC someone. Thanks again! 🙏

Could you share the PCAP file where VAPI is rejecting all of your inbound call requests? This will help you understand what could have been going wrong for you.

Hey Shubham! Thanks for the reply. Since I'm using the hosted version of Vapi (not self-hosted), I unfortunately don’t have access to the network interface where SIP traffic is handled – so I can’t capture a PCAP file from my end. Would you be able to generate a PCAP log on your side while I make a test call to my number (

+4915792320882

)? Let me know if you'd like me to trigger a call at a specific time.

Trigger a new call and share the call ID. I'll look into it.

Hey Shubham, thanks for your help! I just triggered a test call to my SIP trunk number +49 1579 2320882 on Wednesday, April 9th, 2025, at approximately 16:47 CEST from my mobile number +49 176 41259993. Unfortunately, the call did not appear in Vapi's logs, so I couldn't get a Call ID – which is actually the core of the issue: > Vapi seems not to be receiving or registering the INVITE from Sipgate at all. Please let me know if you're able to check internal traffic or logs on your side, or if I should try again at a different time. Thanks again!

Hey, if we get any request unless we reject it, it won't be visible in the dashboard. Most likely, what's happening is you are making the request and VAPI is asking for authorization. Then, either your telephone is returning the wrong credentials or it's not returning the authorization header at all. Because of this, your call eventually gets rejected and it never shows up in the dashboard. What you can do next here is you can share the PCAP file with me from your telephony. I can let you know exactly what you are missing - if it's the authorization header or something else. For your information, the authorization header requires a username and password. Here, the password can be anything except being empty whitespace, and the username has to be your SIP username in VAPI.

Hey Shubham, thanks again for your reply earlier. I’d like to follow up on the ongoing issue we discussed. Since your last message, I’ve gone through a full verification process based on your guidance, and I believe we’ve narrowed the issue down further: 🔄 What I've done so far: ✅ Verified all SIP credentials Username: 2513697e40 SIP domain: sipgate.de Protocol: UDP, Port 5060 Registration status: ✅ Successful — Sipgate dashboard confirms that Vapi’s public IP 44.229.228.186 is registered and online. 📞 Incoming call tests from my mobile number Still getting the message: "The desired contact is currently not available." No incoming call shows up in Vapi’s call logs. 🧪 Zoiper test with the exact same SIP credentials Zoiper receives calls successfully, confirming credentials and SIP trunk are functional. 📡 Wireshark packet analysis Filter: sip || rtp || udp.port == 5060 No new INVITE packets appear in Wireshark when I call the number assigned to Vapi. Only OPTIONS and REGISTER packets are visible — no INVITE ever reaches the Vapi IP during real phone calls. 🔁 Reset everything on both ends Deleted and recreated the SIP configuration in Vapi. Changed the SIP password at Sipgate and updated it in Vapi. Verified that Zoiper was uninstalled and fully disconnected from the SIP account. Reassigned BYO number in Vapi and linked it to the correct agent. Tested using mobile hotspot in addition to Wi-Fi, to rule out local firewall/NAT issues. 📌 Current Situation Vapi is registered and recognized as a connected SIP device on Sipgate. Zoiper works, but Vapi still doesn't receive INVITE packets. No calls appear in Vapi logs. Wireshark confirms: INVITE is never sent by Sipgate to Vapi's IP, even though registration is successful. Would really appreciate your help in figuring out why Sipgate never sends the INVITE to Vapi, despite the trunk appearing online.

Hey buddy, if Sipgate doesn't send an invite request to VAPI, I suggest checking the Sipgate dashboard core logs or other available logs. If you do, try contacting their support team; their system is opaque to us. Without a PCAP file or other information, I can't help you further.

Hey Shubham, here's a full summary – because I believe the root cause is now clearly on the Vapi side. My SIP trunk to Sipgate is online (confirmed by both IP and registration). Sipgate sends the INVITE request correctly to Vapi (44.229.228.186:5060). Vapi responds with 503 Service Unavailable and this message: Reason: Multiple accounts are attempting to default route this carrier I only have one Assistant connected to this number in Vapi (+49 1579 2320882). I tested everything: changed passwords, rebuilt the SIP, removed and re-imported the number. I only have one account with this number active, as visible in the screenshot. The incoming call comes from my private mobile number, not from within Sipgate. Conclusion: Sipgate sends the call to Vapi successfully. But Vapi rejects it internally with this “Multiple accounts” error. Could you please check on your side what is causing this mismatch, or force-clear any internal routing conflicts? I’m happy to send any additional info if needed. Thanks a lot 🙏 https://cdn.discordapp.com/attachments/1358749941010272286/1361305280188649612/Screenshot_2025-04-14_132054.png?ex=67fe45d6&is=67fcf456&hm=bb5f8fef909668da1e03b63ceacd63d44c70fb64ffa2ce38e6345abcb379d9b2& https://cdn.discordapp.com/attachments/1358749941010272286/1361305280666927245/Screenshot_2025-04-14_130706.png?ex=67fe45d6&is=67fcf456&hm=6a46b00fe13da87ca5e3cd5a31780e7e610ad6a10ffff574596bc31bb577ef9c&

Hey, we are looking into it and will get back to you once it is fixed. Meanwhile, can you send me your credential_id and signaling IP address in DM?

Hey Sahil, sure – just to reiterate (although I already shared it in my last message): credential_id: 2513697e40 Signaling IP: 44.229.228.186:5060 The screenshots you asked for were already included above. I just added them again in case you missed them. (Also your DMs are closed, i cant even see the "message" botton.)

@Nir S (CEO/Founder @Cloudonix) can you help him out as well? He is also facing kinda similar issue.

Sure, @H² when are you available for a more "private" conversation, as I will need some "private" information from you in order to help

Holy Vapi, what is going on 😮

👍

Thanks Sir@Nir S (CEO/Founder @Cloudonix) for helping.

Hi, I'm experiencing a similar issue with 3CX and a direct SIP connection. Outbound calls from Vapi work without issues, but inbound calls aren't responding in Vapi, even though the device is correctly registered and online in 3CX. Any idea where I could start looking? Thanks.

@schwalbe 3CX is one of the most horrific pieces of PBX software I've seen - it is so limiting, it's not funny. Everything requires more and more licensing. In any case, please explain your complete call-flow, so I can have a better understanding. Also, you can pin a meeting on my calendar here - https://calendly.com/cloudonix/cloudonix-vapi-integration

@Nir S (CEO/Founder @Cloudonix) If I buy a cloudonix subscription, could you help us integrating sipgate and other providers?

In short - yes