# Configuring Twilio Register Based Trunk

Before proceeding with the next steps, you need to [purchase a DID on Twilio](/portsip-communications-solution/configuring-sip-trunks/twilio-sip-trunk/purchase-a-did-on-the-twilio.md).

***

### Create a SIP Trunk on the Twilio Platform

To create a new SIP trunk on the Twilio platform, follow these steps:

1. Sign in to your [Twilio Console](https://console.twilio.com/).
2. From the left-hand navigation bar, go to **Elastic SIP Trunking**
   * Alternatively, click the **Elastic SIP Trunking** icon in the left vertical navigation bar.
3. Navigate to **Manage > Trunks**.

<figure><img src="/files/PuLZi8gjmWSkmbgKI4v0" alt=""><figcaption></figcaption></figure>

4. Click **Create new SIP Trunk**.
5. Enter a **friendly name** for the trunk, then click **Create**.

<figure><img src="/files/tA2wSENDUN7XpMkQvquY" alt="" width="563"><figcaption></figcaption></figure>

***

### Configure Trunk Termination

After creating the SIP trunk, leave all settings on the **General** page unchanged and proceed to the **Termination** section.\
This section defines where outbound calls from PortSIP PBX are sent to Twilio.

<figure><img src="/files/BHjQfFkU53KUJiFa9z9m" alt=""><figcaption></figcaption></figure>

#### Step 1: Configure the Termination SIP URI

1. In the **Termination** section, enter a **unique Termination SIP URI** of your choice.
2. If the URI is displayed as **Available** (shown in green), it is valid and can be used.

> ❗**Important**\
> Note the full Termination SIP URI (for example, `portsip-pbx.pstn.twilio.com`).\
> This value will be required later when configuring the SIP trunk in **PortSIP PBX**.\
> Your URI must be unique and will differ from the example shown here.

<figure><img src="/files/aII9w17cJomXrT6VEaQx" alt=""><figcaption></figcaption></figure>

***

#### Step 2: Configure Authentication (IP ACL)

1. Scroll down to the **Authentication** section.
2. Under **IP Access Control Lists (IP ACLs)**, create a new ACL entry.
3. Add the **public static IP address of your PortSIP PBX**.
   * You can find this IP address on the **PortSIP PBX Home** page.

> ❗**Best Practice**\
> IP-based authentication improves security by ensuring that only your PBX is allowed to send traffic to Twilio.

<figure><img src="/files/54r9rErJ7NCYVOBNM1IS" alt="" width="563"><figcaption></figcaption></figure>

***

#### Step 3: Configure Credential List (Optional / Recommended)

1. In the **Credential List** section, create a **username and password** pair.
2. Save the credentials.
3. Click **Create** to save the Termination configuration.
4. Once completed, navigate to the **Origination** page to continue the Twilio trunk setup.

> ❗**Note**\
> These credentials will also be used later when configuring the **Twilio SIP trunk in PortSIP PBX**.

<figure><img src="/files/OqC9JM9hitU7BCagMJtZ" alt="" width="563"><figcaption></figcaption></figure>

***

### Configure Trunk Origination

In the **Origination** section, you define how inbound calls from **Twilio** are routed **to PortSIP PBX**.

You will add one or more **Origination SIP URIs** that point to your PortSIP PBX.

> ❗**Prerequisite**\
> Ensure your PortSIP PBX has a **static public IP address or FQDN**.\
> This information is available on the **PortSIP PBX Web Portal Home** page.

***

#### Step 1: Add the Primary Origination URI (US1)

1. In the **Origination** section, locate the **Origination SIP URI** configuration.
2. Enter the SIP URI in the following format (replace with your own PBX IP or FQDN):

   ```
   sip:151.101.2.3;region=us1
   ```
3. Set the following values:
   * **Priority**: `10`
   * **Weight**: `10`
4. Click **Add**.

> ❗**Explanation**\
> This configuration routes inbound SIP traffic from the **Twilio US1 (Virginia)** data center to your PortSIP PBX and restricts origination to that region.

<figure><img src="/files/W5gzMuvhqLNG8q0kYTSc" alt="" width="563"><figcaption></figcaption></figure>

***

#### Step 2: Add a Secondary Origination URI (US2 – Failover)

To provide regional redundancy, add a secondary Origination URI:

1. Click the **plus (+)** icon next to **Origination URI**.
2. Enter the following SIP URI (replace with your own PBX IP or FQDN):

   ```
   sip:151.101.2.3;region=us2
   ```
3. Set the following values:
   * **Priority**: `20`
   * **Weight**: `10`
4. Click **Add**.

> **Explanation**\
> This URI allows Twilio to route inbound calls from the **US2 (Oregon)** data center **only if** the primary US1 region is unable to deliver the call.

<figure><img src="/files/83h5pZjVoa8s3YlhOhtT" alt="" width="563"><figcaption></figcaption></figure>

#### Expected Result

* Inbound calls from Twilio will first attempt delivery via **US1 (Virginia)**.
* If US1 is unavailable, calls will automatically fail over to **US2 (Oregon)**.
* PortSIP PBX will receive inbound SIP traffic securely and predictably.

***

### Assign DID Numbers to Your Elastic SIP Trunk

After creating the Elastic SIP Trunk, you must assign one or more DID numbers to it.

Follow these steps in the **Twilio Console**:

1. From the left-hand navigation menu, go to\
   **Phone Numbers > Manage > Active Numbers**.
2. Click the **phone number** you want to assign to the SIP trunk.
3. On the number details page, locate the **Voice Configuration** section.
4. For **Configure with**, select **SIP Trunk**.
5. In the **SIP Trunk** drop-down list, choose the **Elastic SIP Trunk** you created earlier.
6. Click **Save Configuration**.

The selected DID number is now **associated with your Elastic SIP Trunk**. Inbound calls to this number will be routed through the SIP trunk to **PortSIP PBX**.

<figure><img src="/files/sj6jsWEkkQ6djX0cdvaf" alt=""><figcaption></figcaption></figure>

***

### Configure the Twilio Register-Based Trunk in PortSIP PBX

The **Twilio Register-Based Trunk** corresponds to a **Register-Based Trunk** in PortSIP PBX.

You can configure this trunk at **either** of the following levels:

* **System Administrator level**
  * The trunk can be **shared with one or more tenants**.
* **Tenant Administrator level**
  * The trunk can be **used only by that tenant** and cannot be shared.

***

#### Step 1: Create the Register-Based Trunk

1. Sign in to the **PortSIP PBX Web Portal** as a **System Administrator** or **Tenant Administrator**.
2. From the left-hand navigation menu, go to **Call Manager > Trunks**.
3. Click **Add**, then select **Register Based Trunk**.

<figure><img src="/files/dvJjzdHP0zLdeNfvozXe" alt=""><figcaption></figcaption></figure>

***

#### Step 2: Configure Basic Trunk Settings

Enter the following information:

* **Name**\
  Enter a friendly name for the trunk (for example, `Twilio-Reg-Trunk`).
* **Brand**\
  Select **Twilio**.
* **DID Pool** *(Tenant Admin level only)*\
  If you are configuring the trunk at the **Tenant Administrator level**, specify the Twilio DID numbers assigned to this tenant.

  > ❗**Important**
  >
  > The tenant can use **only the DID numbers in its DID pool** to:
  >
  > * Create inbound and outbound call rules
  > * Configure outbound caller IDs for extensions

**DID Pool Format Examples**

```
12027594810
12027594810;12027594815
12027594810-12027594815;12027594820
12027594810-12027594815;12027594830-12027594845
```

* **Hostname or Address**\
  Enter the **Twilio Trunk Termination URI** created earlier, for example:

```
portsip-pbx.pstn.twilio.com
```

Click **Next** to continue.

<figure><img src="/files/NgTOttKZkssEytwrHZG3" alt=""><figcaption></figcaption></figure>

***

#### Step 3: Configure Authentication Credentials

1. Enter the **Authentication Name** and **Password** that were created earlier in the **Twilio Credential List**.
2. Click **Next**.

<figure><img src="/files/Q85JbudxOydzvKeWpKFW" alt=""><figcaption></figcaption></figure>

***

#### Step 4: Configure Trunk Options

* **Need Registration**\
  **Disable** this option.

  > ❗Twilio Elastic SIP Trunking does **not** accept SIP `REGISTER` messages.
* **Max Concurrent Calls**\
  Defines the maximum number of simultaneous calls that PortSIP PBX can establish using this trunk.
  * Adjust this value according to your Twilio capacity and expected call volume.

Leave all other settings at their default values unless you have specific requirements.

Click **Next** to continue.

<figure><img src="/files/JUeAJzxMv3V0mIdWDMrf" alt=""><figcaption></figcaption></figure>

***

#### Step 5: Assign Tenants and DID Pool *(System Admin level only)*

> ❗**Note**\
> This step is available **only** when configuring the trunk at the **System Administrator level**.

1. Assign the trunk to one or more tenants.
2. Provide Twilio DID numbers to each tenant using the **DID Pool**.

> ❗**Important**
>
> * Each DID can be assigned to **only one tenant**.
> * A tenant can use **only the DID numbers in its DID pool** to:
>   * Create inbound and outbound call rules
>   * Configure outbound caller IDs for extensions

**DID Pool Format Examples**

```
12027594810
12027594810;12027594815
12027594810-12027594815;12027594820
12027594810-12027594815;12027594830-12027594845
```

Click **OK** to save the configuration.

<figure><img src="/files/xIWL5FlnXRAhafSLv2g2" alt=""><figcaption></figcaption></figure>

***

#### Expected Result

* The trunk configuration is now complete.
* Because **Need Registration** is disabled, the trunk status will **always display as Online** in the trunk list. This is expected and correct behavior for Twilio Elastic SIP Trunks.

<figure><img src="/files/VkuvoF1PqrlxLDT1Diy9" alt=""><figcaption></figcaption></figure>

***

### Next Steps

* Refer to[ Twilio Elastic SIP Trunking](https://www.twilio.com/docs/sip-trunking) documentation for platform-specific details.
* Proceed to [Configuring inbound and outbound calls](/portsip-communications-solution/configuring-sip-trunks/twilio-sip-trunk/configuring-outbound-and-inbound-calls.md) in PortSIP PBX.


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