# Create a SIP Register Trunk

A SIP (Session Initiation Protocol) register trunk connects your phone system to an internet telephony service provider (ITSP) by authenticating with a username and password. A trunk is the connection that carries calls between your phone system and your provider; a register trunk logs in to the provider with credentials, much like a phone registers, so the provider knows where to send incoming calls. Use this walkthrough as a general model: the steps and fields apply to any SIP register trunk, regardless of provider.

## Example account details

Throughout this guide, assume you have purchased a SIP account from a provider named ABC. Your provider gives you a set of connection details similar to the following:

| Setting | Value |
| --- | --- |
| Provider domain | abc.provider.com |
| Protocol | SIP |
| Registration port | 5060 |
| Transport | UDP |
| Username | 254258255 |
| Authentication name | 254258255 |
| Password | 05JsOmsIS54SYh |

Substitute your own provider's values wherever the example values appear below.

## Before you begin

- You have an active SIP account from an ITSP, and the provider has supplied a username and password.
- Your phone system can reach the ITSP over the network.
- Your account has permission to add trunks.

:::note
If the **Add** button under **Extension and Trunk > Trunk** is greyed out, your account cannot add trunks. Contact your service provider to have the permission granted.
:::

## Add the trunk

1. Sign in to the management portal and go to **Extension and Trunk > Trunk**, then click **Add**.

2. Under **Basic**, fill in these fields:
   - **Name**: A label that helps you recognize the trunk later.
   - **Trunk Status**: Choose **Enabled**.
   - **Select ITSP Template**: Choose **General**.

3. Under **Detailed Configuration**, set the trunk type and enter the SIP credentials from your provider:
   - **Trunk Type**: Choose **Register Trunk**.
   - **Transport**: Match the transport your provider uses. In this example, choose **UDP**.
   - **Hostname/IP**: The provider's domain name or IP address. In this example, enter `abc.provider.com`.
   - **Port**: The registration port your provider gave you. In this example, enter `5060`.
   - **Domain**: The domain used in the SIP URI of headers such as From and To. In this example, enter `abc.provider.com`.
   - **Username**: The username from your provider. In this example, enter `254258255`.
   - **Password**: The password from your provider. In this example, enter `05JsOmsIS54SYh`.
   - **Authentication Name**: The authentication name from your provider. In this example, enter `254258255`.

   :::caution
   The transport you choose (UDP, TCP, or TLS) must match what your provider expects. If it does not match, the trunk will not register and no calls will pass over it.
   :::

   :::note
   If your provider did not supply a separate domain, enter the same value you used for **Hostname/IP**. The authentication name is usually identical to the username.
   :::

   **Enable Outbound Proxy** is optional. When a trunk uses an outbound proxy, every SIP packet for outbound calls placed over that trunk is routed through the proxy server first.

   :::note
   Check with your ITSP about whether it supports an outbound proxy, and configure the proxy settings according to the provider's instructions.
   :::

4. Open the **DIDs/DDIs** tab to assign DID numbers to the trunk. A DID (Direct Inward Dialing, called DDI or Direct Dialing Inward outside North America) is a phone number your provider routes to your system so external callers can reach it. Click **Add**, then create the numbers you need.

   To add a single DID number:
   1. In the **Create Method** list, choose **Single DID**.
   2. Set these fields:
      - **DID/DDI**: The DID number from your provider.
      - **DID/DDI Name**: Optional. A name that helps you tell inbound calls apart by DID number. When someone dials this number, the name appears on the called party's device.

   To add a range of DID numbers:
   1. In the **Create Method** list, choose **DID Range**.
   2. Set these fields:
      - **DID Range**: The first and last numbers in the range.
      - **DID/DDI Name**: Optional. A name that helps you tell inbound calls apart by DID number. When someone dials a number in the range, the name appears on the called party's device.

   When finished, click **Confirm**.

   :::tip
   For more detail on DID options, see [Configure DID Numbers on a Trunk](/pbx/administrator-guide/configure-did-numbers-on-a-trunk/).
   :::

5. Optional. Use the **Advanced**, **Inbound Caller ID Reformatting**, **Outbound Caller ID**, or **SIP Headers** tabs to adjust additional behavior.

6. Click **Save**, then **Apply**.

## Confirm registration

Return to **Extension and Trunk > Trunk** and review the trunk on the list.

When the status shows the registered icon ![Trunk registered indicator](/images/pbx/trunk-ok.png), the trunk has registered with the provider successfully.

For a breakdown of every SIP trunk state, see [SIP Trunk status](/pbx/administrator-guide/sip-trunk-overview/#concept_kzd_png_tdb__section_b1z_1ft_wpb).

## Next steps

- To receive calls over this trunk, assign it to one or more inbound routes. See [Set up an Inbound Route](/pbx/administrator-guide/set-up-an-inbound-route/).
- To place calls over this trunk, assign it to one or more outbound routes. See [Set up an Outbound Route](/pbx/administrator-guide/set-up-an-outbound-route/).