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

# Create SIP trunk

> Create a new SIP trunk with credentials, address, and proxy settings

This endpoint creates a new SIP trunk. The platform automatically provisions inbound and outbound trunks on the voice infrastructure using the provided credentials.

### Body Parameters

<ParamField body="sip_trunk_type" type="string" required>
  The type of SIP trunk: `extension` for a SIP extension, or `number` for a phone number (DID). This determines the expected format of the `phone_number` field.
</ParamField>

<ParamField body="phone_number" type="string" required>
  The SIP extension (1-15 characters, e.g. `1000`) when `sip_trunk_type` is `extension`, or a phone number in E.164 format (e.g. `+14155551234`) when `sip_trunk_type` is `number`.
</ParamField>

<ParamField body="nickname" type="string" optional>
  A short, human-friendly label for the trunk (e.g. "Provider X — Main"). Maximum 50 characters.
</ParamField>

<ParamField body="sip_username" type="string" required>
  Username for SIP authentication (3-128 characters)
</ParamField>

<ParamField body="sip_password" type="string" required>
  Password for SIP authentication (minimum 3 characters)
</ParamField>

<ParamField body="sip_address" type="string" required>
  The SIP server address without port (e.g. `sip.provider.com`)
</ParamField>

<ParamField body="sip_calling_format" type="string" required>
  The outbound calling number format:

  * `+e164` — International with `+` prefix (e.g. `+12025550123`)
  * `e164` — International without `+` prefix (e.g. `12025550123`)
  * `national` — National format without country code (e.g. `0741926265`)
</ParamField>

<ParamField body="inbound_authorization_type" type="string" required>
  How inbound calls are authenticated:

  * `auth` — Uses the same SIP username and password configured for outbound
  * `ip` — Whitelists specific IP addresses (requires `allowed_inbound_ips`)
</ParamField>

<ParamField body="allowed_inbound_ips" type="array" optional>
  Array of IP addresses allowed to send inbound calls. **Required** when `inbound_authorization_type` is `ip`. Must contain at least one valid IP address.
</ParamField>

<ParamField body="country_code" type="string" required>
  ISO 3166-2 country code where the SIP trunk is located (e.g. `US`, `GB`, `DE`). When `sip_trunk_type` is `number`, the country is auto-detected from the phone number if possible.
</ParamField>

<ParamField body="outbound_proxy" type="boolean" optional>
  Route outbound calls through a fixed IP address. Default: `false`. Only enable this if your SIP provider requires IP-based authentication for outbound traffic.
</ParamField>

### Response

<ResponseField name="message" type="string">
  Success message
</ResponseField>

<ResponseField name="data" type="object">
  The created SIP trunk object (same fields as [Get SIP trunk](/api-reference/sip-trunks/get-sip-trunk))
</ResponseField>

<ResponseExample>
  ```json 201 Extension with password auth theme={null}
  {
    "message": "SIP trunk created successfully.",
    "data": {
      "id": 42,
      "phone_number": "1000",
      "nickname": "Provider X — Main",
      "sip_username": "myuser",
      "sip_address": "sip.provider.com",
      "sip_calling_format": "+e164",
      "inbound_authorization_type": "auth",
      "allowed_inbound_ips": null,
      "outbound_proxy": false,
      "country_code": "US",
      "inbound_trunk_id": "ST_xxxxxxxxxxxx",
      "outbound_trunk_id": "ST_yyyyyyyyyyyy",
      "created_at": "2026-03-31T10:00:00.000000Z",
      "updated_at": "2026-03-31T10:00:00.000000Z"
    }
  }
  ```

  ```json 201 Phone number (DID) with IP auth theme={null}
  {
    "message": "SIP trunk created successfully.",
    "data": {
      "id": 43,
      "phone_number": "+14155551234",
      "nickname": null,
      "sip_username": "trunk_user",
      "sip_address": "sip.provider.com",
      "sip_calling_format": "e164",
      "inbound_authorization_type": "ip",
      "allowed_inbound_ips": ["203.0.113.10", "198.51.100.20"],
      "outbound_proxy": true,
      "country_code": "US",
      "inbound_trunk_id": "ST_xxxxxxxxxxxx",
      "outbound_trunk_id": "ST_yyyyyyyyyyyy",
      "created_at": "2026-03-31T10:00:00.000000Z",
      "updated_at": "2026-03-31T10:00:00.000000Z"
    }
  }
  ```

  ```json 409 Duplicate theme={null}
  {
    "error": "A SIP trunk with the same phone number, username, and address already exists."
  }
  ```

  ```json 422 Validation Error theme={null}
  {
    "message": "The given data was invalid.",
    "errors": {
      "sip_address": ["SIP server address is required."],
      "sip_calling_format": ["SIP calling format must be one of: +e164, e164, national."]
    }
  }
  ```

  ```json 500 Provisioning Error theme={null}
  {
    "error": "Failed to create SIP trunk. Please try again or contact support."
  }
  ```
</ResponseExample>

### What happens after creation

When you create a SIP trunk, the platform automatically:

1. **Provisions an inbound trunk** on the voice infrastructure — using either username/password or IP-based authentication depending on your `inbound_authorization_type` setting
2. **Provisions an outbound trunk** — using the SIP address and credentials you provided, optionally through the outbound proxy

If provisioning fails, the SIP trunk is not saved and a `500` error is returned.

### Next steps

After creating a SIP trunk, assign it to an AI assistant:

* **[Create Assistant](/api-reference/assistants/create-assistant)** — Use the `phone_number_id` parameter
* **[Update Assistant](/api-reference/assistants/update-assistant)** — Change the phone number on an existing assistant