Static IP / CIDR for SIP trunk integration with Japanese carrier

Support Help
1

Hello Retell AI Support Team,

I’m setting up a SIP trunk integration with a Japanese
telephony provider (LIPSE / IPS Pro Co., Ltd.) for inbound
voice calls to my Retell AI agent.

The Japanese provider requires a static IP address or CIDR
range for their firewall whitelist (they cannot accept
dynamic IPs).

I found “18.98.16.120/30” in your Twilio integration docs.
Could you please confirm:

  1. Is this CIDR block applicable for any SIP trunk provider,
    or only Twilio?
  2. Are there other static IP ranges I should provide for
    Japan-region calls?
  3. For “Dial to SIP Endpoint” method, what static IPs would
    the calls originate from?

My use case: Inbound calls only, Japan, single phone number,
expected ~50 calls/month.

Thank you for your support.

Best regards,
Hiroki

2

Hey @h-kotera

The IP block 18.98.16.120/30 applies to all SIP trunk providers (all regions), not just Twilio. It’s the IP block to whitelist for traffic to Retell’s SIP server.

Additional ranges exist only for certain US traffic (143.223.88.0/21, 161.115.160.0/19). For Japan inbound, 18.98.16.120/30 is what you’d provide to LIPSE.

For Dial to SIP URI method, the same Retell SIP server (sip:sip.retellai.com) and IP block apply — your telephony provider dials into Retell, so whitelist the same 18.98.16.120/30 on their side

For more details you can see ( Custom Telephony Overview - Retell AI ) Guide

Thank You