Hi everyone, I’m trying to configure a BYO SIP trunk in Vapi with a SIP provider that requires SIP Registration over TLS/SRTP, but outbound calls are failing with: call.in-progress.error-sip-outbound-call-failed-to-connect SIP provider requirements The provider requires SIP REGISTER with: Domain / Registrar: voice.xxxxxxx.cl Port: 5061 Transport: TLS Media: SRTP Username: myuser Password: mypassword Realm: voice.xxxxxxx.cl Expires: 3600 They expect something like: REGISTER sip:voice.xxxxxxx.cl:5061 SIP/2.0 To: sip:myuser@voice.xxxxxxx.cl:5061 From: sip:myuser@voice.xxxxxxx.cl:5061 Contact: sip:myuser@PUBLIC_IP:5061 Allowed codecs: G722 G711a G729 DTMF: RFC2833 / RFC4733 payload 101 --------------------------------------------- My Vapi SIP trunk configuration Name: Test SIP Trunk Gateway #1 IP Address / Domain: voice.xxxxxxx.cl Port: 5061 Protocol: tls/srtp Netmask: 32 Direction: Outbound Only Options Ping: Disabled Gateway #2 IP Address / Domain: 190.xxx.xxx.xxx Port: 5061 Protocol: tls/srtp Netmask: 32 Direction: Inbound Only Options Ping: Disabled Authentication Username: myuser Password: mypassword SIP Registration Domain: voice.xxxxxxx.cl Username: myuser Realm: voice.xxxxxxx.cl Advanced Settings Leading Plus for Outbound: Enabled Use public IP in Contact header: Enabled Tech Prefix: empty SIP Diversion Header: empty Use Cluster SIP: Disabled Phone number configuration The BYO phone number is associated with this SIP trunk credential. Provider: byo-phone-number Phone Number: +562XXXXXXXX SIP Trunk Credential: Test SIP Trunk Status: active The provider says the service is enabled on their side, the credentials are valid, and there should be no IP blocking. From Vapi, the phone number and SIP trunk credential seem to be associated correctly, but the call still fails immediately with the generic SIP outbound error. Could anyone help me identify what I might be missing or misconfiguring?

This looks less like a credential issue and more like a registration/transport mismatch Vapi often doesn’t maintain persistent SIP REGISTER the way providers expecting strict TLS/SRTP flows require, so the trunk may never be “reachable” from their side. I’d focus on confirming if your provider supports IP-auth (no REGISTER) or if Vapi is actually completing and refreshing registration (check Contact + expiry behavior). Also double-check cipher compatibility + SRTP enforcement, since some providers silently drop on mismatch. Happy to help you debug this directly are you seeing any REGISTER success/401/200 OK flow in logs, or is it failing before that stage? @joaquin

Thanks, that makes sense. From my side, I only see this generic error:

call.in-progress.error-sip-outbound-call-failed-to-connect

The BYO number is associated with the SIP trunk credential, and the call shows

vapi.sip

, but it fails almost immediately. Do you know if Vapi support can check the SIP trace for this specific call and confirm whether REGISTER is completing successfully, what

Contact

/

Expires

are being sent, and whether the outbound INVITE is being rejected? My provider is asking me to share our side of the logs before they continue debugging. Call ID:

019df8e0-cf9e-7000-b077-d25392f3acdd

That kind of immediate outbound failure usually points to a mismatch around TLS/SRTP negotiation or how the registration/contact headers are being handled—I’ve run into similar quirks with SIP providers that are strict on REGISTER flows. Your setup looks close, but there’s likely a subtle detail Vapi isn’t aligning with on their side. Happy to take a closer look with you and pinpoint it quickly. @joaquin

Thanks James, appreciate it 💪 . That’s exactly what I want to validate first. Right now I only see the generic Vapi error, so I don’t know if the issue is REGISTER, TLS/SRTP negotiation, Contact headers, or the outbound INVITE. For the call ID I shared earlier, do you know if Vapi support can check or share the SIP trace? My provider doesn’t support IP auth, so this has to work with SIP Register. I suspect there isn’t much more I can configure on the Vapi side, but if I can at least get the specific SIP error or trace, I can ask my provider whether they can adapt something on their end. @James Christopher @Matt

Yeah, that’s the frustrating part with Vapi you really need the SIP trace to stop guessing. In my experience, their support team can pull detailed logs (including REGISTER + INVITE flow and the exact SIP response codes) if you give them the call ID, even though it’s not exposed in the dashboard. Once you have that, it usually becomes obvious whether it’s a TLS handshake issue, auth challenge, or SDP/SRTP mismatch happy to help you interpret it when you get it. @joaquin

@User help pls 🥲