Hi, I’m currently setting up a SIP integration between a telephony provider and Retell, and I wanted to clarify the expected authentication flow to make sure I’m aligning things correctly. The provider is saying that since they are sending calls to Retell, Retell should generate SIP credentials (us…

Hey @r0wan.muhammed0.o Retell does not generate SIP credentials . Credentials (if any) come from your telephony provider. Inbound (provider → Retell): Routed to sip:sip.retellai.com. The provider should whitelist Retell’s IP block (e.g., 18.98.16.120/30). No SIP credentials are used on Retell’s si…

Hi, thanks for the response! This is not related to a specific call issue, I’m just trying to confirm the correct SIP trunking setup and authentication flow. From my understanding: -- Retell does not generate SIP credentials – Inbound calls (provider → Retell) are handled via routing to sip:sip.…

Thanks a lot for the clear explanation, this really helped! I’ll proceed with the setup accordingly. Really appreciate the help!

SIP trunking clarification for inbound vs outbound authentication

Support Help

mark1 April 23, 2026, 2:46pm 2

Hello @r0wan.muhammed0.o

Could you please share the call ID along with the PCAP file for the call? This will help our team investigate the issue in detail.

Thank you!

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SIP trunking clarification for inbound vs outbound authentication

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