Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.

​ To learn more, see the sources I considered: [[1] Custom Telephony Overview](https://docs.retellai.com/deploy/custom-telephony) ​

### Answer I don't have specific information about IP addresses for transferred calls in the available sources. For general Retell SIP traffic, the IP block is

18.98.16.120/30

for all regions, with additional blocks

143.223.88.0/21

and

161.115.160.0/19

for certain United States traffic. [(1) ]() However, I cannot find documentation specifically addressing IP addresses used during call transfers (warm or cold transfers) . If you need more detailed information about IP addresses for transferred calls, I recommend: - Checking the [Custom Telephony Overview]() - Visiting [Documentation]() - Visiting [Hire certified Retell partner]() Would you like a general answer based on my knowledge instead?

### Answer The IP blocks I mentioned apply globally to all Retell SIP traffic, including Canadian traffic [(1) ]() . The IP ranges are: -

18.98.16.120/30

(all regions) -

143.223.88.0/21

(certain United States traffic) -

161.115.160.0/19

(certain United States traffic) These are the IP blocks you should whitelist for Retell's SIP server traffic . The documentation doesn't specify separate IP ranges for Canadian traffic specifically—the

18.98.16.120/30

block covers all regions globally . For call transfers specifically (whether to Canadian numbers or otherwise) , I don't have documentation detailing separate IP addresses used during the transfer process.

​ To learn more, see the sources I considered: [[1] Custom Telephony Overview](https://docs.retellai.com/deploy/custom-telephony) ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.