> ## Documentation Index
> Fetch the complete documentation index at: https://docs.retellai.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Telnyx

> A step by step guide to connect to your Telnyx account via SIP trunking

<Steps>
  <Step title="Create Elastic SIP Trunking">
    1. Create the trunk, select FQDN as the type, and give it a name.

    <img height="200" src="https://mintcdn.com/retellai/32uO5g9DswfoJ9j7/images/custom-telephony/telnyx/create.jpeg?fit=max&auto=format&n=32uO5g9DswfoJ9j7&q=85&s=a0b5c74d7b0f9d0a27d6a2fb903b232b" data-path="images/custom-telephony/telnyx/create.jpeg" />

    2. Add FQDN

    Add the FQDN of Retell's SIP server: `sip.retellai.com`. Select `SRV` as the
    DNS record type.

    <img height="200" src="https://mintcdn.com/retellai/32uO5g9DswfoJ9j7/images/custom-telephony/telnyx/setting.jpeg?fit=max&auto=format&n=32uO5g9DswfoJ9j7&q=85&s=5c21b0780b66885597c416d98dd8fe1e" data-path="images/custom-telephony/telnyx/setting.jpeg" />

    3. Setup Outbound Calls Authentication

    Select credentials as the authentication method, and add the username and password.
    You will need to use this username and password when importing the number to Retell.

    <img height="200" src="https://mintcdn.com/retellai/32uO5g9DswfoJ9j7/images/custom-telephony/telnyx/outbound-auth.jpeg?fit=max&auto=format&n=32uO5g9DswfoJ9j7&q=85&s=87ba94312ebb879e7dc9b19ed27e5bf6" data-path="images/custom-telephony/telnyx/outbound-auth.jpeg" />

    <Note>
      Telnyx requires the header `X-Telnyx-Username: <username>` to be included in the outbound calls when using credentials as the authentication mechanism.
      See Telnyx [documentation](https://support.telnyx.com/en/articles/5271423-guide-to-sip-anchorsite-settings#h_0b59d6992a) for more details.
      You can find deatils on adding custom SIP headers on [Make Outbound Calls](/deploy/outbound-call#step-2:-make-outbound-calls) page.
    </Note>

    4. Setup Inbound Setting

    * Select `+E.164` as the number format.
    * Select `G722`, `G711U`, `G711A` as the codecs.
    * Select `TCP` as the transport method. (TCP is recommended over UDP due to reliability factors)
    * Select your SIP region.

    <img height="200" src="https://mintcdn.com/retellai/TRHbNQLLwdXdtkVi/images/custom-telephony/telnyx/inbound-setting.jpeg?fit=max&auto=format&n=TRHbNQLLwdXdtkVi&q=85&s=202c89ac9ebd5fe08ae5e24a9698541c" data-path="images/custom-telephony/telnyx/inbound-setting.jpeg" />

    4. Setup Outbound Setting

    Create a new outbound voice profile

    <img height="200" src="https://mintcdn.com/retellai/32uO5g9DswfoJ9j7/images/custom-telephony/telnyx/voice-profile.jpeg?fit=max&auto=format&n=32uO5g9DswfoJ9j7&q=85&s=eb72458506714003dab29aec2140cdbb" data-path="images/custom-telephony/telnyx/voice-profile.jpeg" />

    And select that in the outbound setting

    <img height="200" src="https://mintcdn.com/retellai/32uO5g9DswfoJ9j7/images/custom-telephony/telnyx/outbound-setting.jpeg?fit=max&auto=format&n=32uO5g9DswfoJ9j7&q=85&s=7a33bb6784839e1e0dbb662c4064c5bd" data-path="images/custom-telephony/telnyx/outbound-setting.jpeg" />
  </Step>

  <Step title="Move numbers to Elastic SIP Trunking">
    You've created the elastic SIP trunk, now you would need to purchase numbers / move
    existing numbers to this trunk.

    <img height="200" src="https://mintcdn.com/retellai/32uO5g9DswfoJ9j7/images/custom-telephony/telnyx/assign-number.png?fit=max&auto=format&n=32uO5g9DswfoJ9j7&q=85&s=a7118a51ec9841b2bed9c3d62d5b6a86" data-path="images/custom-telephony/telnyx/assign-number.png" />
  </Step>

  <Step title="Import numbers to Retell">
    Now the number is set up with your elastic SIP trunking, you need to
    import the number to Retell so that we will know how to route the call.

    <img height="200" src="https://mintcdn.com/retellai/32uO5g9DswfoJ9j7/images/custom-telephony/import-number.png?fit=max&auto=format&n=32uO5g9DswfoJ9j7&q=85&s=19c4a219923eb0adc03c807cb8d767c3" data-path="images/custom-telephony/import-number.png" />

    Here you will supply Telnyx's FQDN as the termination SIP URI. You can find your FQDN based on
    your choice of SIP region in this [doc](https://sip.telnyx.com/) (e.g. sip.telnyx.com). You will also need to supply
    the username, password and any additional SIP headers you set up earlier in the outbound authentication as well.

    <img height="200" src="https://mintcdn.com/retellai/32uO5g9DswfoJ9j7/images/custom-telephony/import-number-detail-telnyx.png?fit=max&auto=format&n=32uO5g9DswfoJ9j7&q=85&s=bdd4e9d406b74aa12a779c94c9d8697d" data-path="images/custom-telephony/import-number-detail-telnyx.png" />

    You can also import number programmatically via [Import Number API](/api-references/import-phone-number).

    Now the number is imported, you can make and receive calls with this number just like a number
    you purchased from Retell -- it will show up in your dashboard, and you can make phone calls from
    Dashboard directly. You can also use the [Create Phone Call API](/api-references/create-phone-call)
    to create calls programmatically.
    If you wish to Retell to stop using this number, you can delete it from the dashboard or via
    the [Delete Number API](/api-references/delete-phone-number).
  </Step>
</Steps>