VAPI•8mo ago

Have an issue when setting up SIP trunk in VAPI

I am using my SIP trunk and I need to connect the SIP trunk on VAPI so make it possible to have a call through my SIP trunk phone number.
I tested with my cell phone and microsip and I ensured that SIP trunk is working well, but when I am trying to connect SIP trunk and added my SIP trunk phone number and call that, but the call doesn't reach to VAPI. On my SIP trunk, it show "BUSY".

forward-apricotOP•5/16/25, 12:01 PM

Outbound call is working well, but inbound call is not working. Seems like VAPI rejects the invite from my SIP trunk. How can I solve this???

military-pink•5/16/25, 12:12 PM

same issue here calls are not connecting to sip url which ends with sip:<unique-url>@sip.vapi.ai that I've created as a part of SIP Telephony

military-pink•5/16/25, 12:12 PM

@Vapi Team

forward-apricotOP•5/16/25, 1:51 PM

thanks for your reply, you didn't solve the issue yet?

military-pink•5/16/25, 2:40 PM

not solved

then-purple•5/16/25, 4:39 PM

Have the same issue

then-purple•5/16/25, 4:43 PM

401 Unauthorized 44.238.177.138 → us.wavix.net (209.58.144.243) 2025-05-16 12:04:01 UTC
SIP/2.0 401 Unauthorized
Via: SIP/2.0/UDP 209.58.144.243;branch=z9hG4bK80ac.670110536099f59bbfeb0df08763f96b.0;rport=5060
Via: SIP/2.0/UDP 209.58.147.214:5080;received=209.58.147.214;branch=z9hG4bK54252bb2;rport=5080
From: +14388606204 <sip:+14388606204@209.58.144.243>;tag=as54197fb8
To: +15144189967 <sip:+15144189967@sip.vapi.ai>;tag=3QrFc9cNDF4aH
Call-ID: 67acd8ac1d6b7d9149013e2e5d4160a8@209.58.147.214:5080
CSeq: 102 INVITE
WWW-Authenticate: Digest realm="sip.vapi.ai", algorithm=MD5, qop="auth", nonce="174739704125100"
Content-Length: 0

VapiAPP•5/17/25, 4:26 AM

Hey,

Could you please schedule a brief call at your convenience so we can discuss this matter in detail?

Kindly use the following link to book a suitable time: https://calendly.com/shubham-vapi/chat-30m.

military-pink•5/17/25, 5:30 AM

Hi @Shubham Bajaj, I am not able to find any slots nearby the latest slot is in june. For us we are working on a client project and this issue is creating extension in our timeline. If we can connect for a 10 min call on Monday/Tuesday/Wednesday, that would be helpful.

inner-olive•5/17/25, 11:38 PM

Hi guys, I'm not an expert but I had this issues before and maybe the experience could help a bit. Let me share my thoughts with each of you

Mmilitary-pink same issue here calls are not connecting to sip url which ends with sip:<unique-...

inner-olive•5/17/25, 11:41 PM

In this case, I'd like to recheck what do you mean.
When you create a <unique-url>@sip.vapi.ai in your Vapi account you should connect your incoming call to it. You should send your call to this SIP URI from your PBX (or whatever you have). You shouldn't register an endpoint with it, just send the call.
Let me know if im on the right track with it

Tthen-purple 401 Unauthorized 44.238.177.138 → us.wavix.net (209.58.144.243) 2025-05-16 12:04...

inner-olive•5/17/25, 11:45 PM

In this case, I'm not 100% sure which is your use case, but I assume that you are trying to make a call from your device +14388606204 to your Vapi registered +15144189967.
If thats right and you are receiving an Unauthorized, first of all remember that Vapi doesnt need any password to be specified to connect a inbound call, so check that in your SIP URI or SIP destination you are not specifying a password. And then, I can see that is setting realm as the domain, just make sure that you are using the same realm on both sides or just delete it to test it first.

Fforward-apricot I am using my SIP trunk and I need to connect the SIP trunk on VAPI so make it p...

inner-olive•5/17/25, 11:50 PM

And this last but not least different question in just one case

Although, It was the first one.

Well, I would need more context about how are you getting these configs done, but if I'm right you are trying to call from your SIP number (that is working and can receive external calls and make outbound calls to other SIP destinations) to a Vapi number and you are receiving Busy from Vapi.
In this case, I would first check that you have properly configured your Vapi phone number and the assistant asigned, then check from where the sip endpoint is trying to call if you can reach sip.vapi.ai 5060 and check it also from your PBX source. You can use a telnet tool to verify that.

Hope it helps!

VapiAPP•5/19/25, 10:59 PM

Hey,

You can check out this guide: https://docs.vapi.ai/advanced/sip/sip-trunk for details on integration.

Note: This is a standard guide used by many telephony providers, so it should be helpful. Let me know if you have any questions that are not answered in this documentation

forward-apricotOP•5/20/25, 6:19 AM

I think it is successfully set up because outbound call is working well, but inbound call is not working. It sends "Invite" request but failed.

VapiAPP•5/20/25, 10:48 PM

Can you provide a call id for the inbound calls and the assistant id?

Have an issue when setting up SIP trunk in VAPI

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