### Answer --- When configuring the Call Transfer Node with dynamic routing and extensions, here's what you need to know: Transfer Number Format Set the transfer number to be either a number in e.164 format, or a SIP URI in the format of

sip:username@domain

(e.g.,

sip:user@retellai.com

) , or use a dynamic variable that gets substituted at runtime. [(1) ]() Adding Extensions Set the transfer number extension if needed. Extension must be 0-9, '*', '#' (e.g.,

123#

) . Dynamic Routing Setup For dynamic routing, you can use dynamic variables with the

{{variable_name}}

syntax. [(2) ]() For example, you might prompt your agent: "If the user wants to reach support, transfer to +1415xxxxxxx; if the user wants to reach sales, transfer to +1213xxxxxxx." [(3) ]() Practical Steps: 1. In your Call Transfer Node, set the "Transfer To Target" as a dynamic variable (e.g.,

{{transfer_target}}

) . [(1) ]() 2. Configure the extension field separately with the appropriate digits (0-9, '*', '#') . 3. Ensure phone numbers are in E.164 format (e.g.,

+12137771234

) . [(4) ]() 4. Update your prompt to instruct the agent when to use which number based on caller needs. [(5) ]() If you're using dynamic variables, make sure to pass the values at runtime via the API or set default values at the agent level. [(2) ]()

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] Call Transfer Node](https://docs.retellai.com/build/conversation-flow/call-transfer-node) [[2] Dynamic Variables](https://docs.retellai.com/build/dynamic-variables) [[3] AI Phone Call Routing: How It Works | Retell AI](https://www.retellai.com/blog/ai-call-routing-how-does-it-really-work) [[4] Routing Calls to Dynamic Number](https://discord.com/channels/1186424376300679209/1346575575963144273) [[5] Transfer the Caller directly on the vendor number found on Knowledge base..](https://discord.com/channels/1186424376300679209/1395497284510417036) ​