Dear Vapi Team, I am a customer of the VoIP provider DIDlogic and am currently trying to use the “Bring Your SIP Trunk Carrier” integration. During the setup, I encountered an issue: when I enter the FQDN of the DIDlogic SIP gateways (sip.lax.didlogic.net or sip.nyc.didlogic.net), I receive the following error: “Failed to create SIP trunk credential.” However, if I replace the FQDN with the corresponding IPv4 address, the SIP trunk is created successfully without any errors. Back in September 2025, I set up Vapi for another project and did not experience this issue. Could you please investigate and address this problem? Thank you in advance for your assistance. https://cdn.discordapp.com/attachments/1447585163000156192/1447585163780554913/0.png?ex=6980aabd&is=697f593d&hm=afa745a8c9080ce2abf2b6c55350842a85bfe3ecadad62d462698e889881ca84&

Vapi supports using FQDNs (like

sip.lax.didlogic.net

) for SIP trunk gateways, as shown in the documentation. However, if you encounter a "Failed to create SIP trunk credential" error with an FQDN, but not with an IP address, this may indicate a temporary DNS resolution or platform issue not covered in the documentation. As a workaround, continue using the IP address for now and contact Vapi support with your error details and configuration for further investigation. Example (using IP address):

json
{
  "provider": "byo-sip-trunk",
  "name": "DIDlogic",
  "gateways": [
    { "ip": "23.19.63.1", "inboundEnabled": false }
  ],
  "outboundAuthenticationPlan": {
    "authUsername": "92525",
    "authPassword": "YOUR_SIP_PASSWORD"
  }
}

For reference, see the [SIP trunk setup guide](https://docs.vapi.ai/advanced/sip/sip-trunk). Source: - [SIP Trunking Vapi Documentation](https://docs.vapi.ai/advanced/sip/sip-trunk)

I'm having the same issue.

with DIDlogic?

No - with another VOIP provider, but I'm unable to enable to create the trunk with both FQDN and with inbound enabled. How did you resolve?

replaced with ipv4

Ah - yeah, that won't work for me, my VoIP provider mandates FQDN for internal routing. Thanks for getting back to me.

Has anyone got a step by step on how to connect DIDlogic to VAPI ?

@Kambo007 https://didlogic.com/setup/setup-guides/other-guides/vapi-ai-setup-guide/#setting-up-phone-number-via-sip-trunking here is the guide