# Retell AI

Use [Retell AI voice agents](https://www.retellai.com/) with **DIDWW SIP Trunking** to handle inbound and outbound
calling over standard phone lines.
Connect your DIDWW SIP trunks with Retell AI to route incoming calls to AI agents, place outbound calls through DIDWW
trunks, and manage voice conversations using your existing DIDWW phone numbers.

- Route incoming calls from DIDWW numbers to Retell AI agents.
- Connect callers to AI agents for real-time conversations.
- Import existing DIDWW numbers into Retell AI.

- Place outbound calls through DIDWW Outbound Trunks.
- Assign inbound and outbound AI agents to DIDWW numbers.
- Manage voice conversations over standard phone lines.

---

## 1. Route Incoming Calls to Retell AI

Configure an Inbound SIP Trunk in the DIDWW User Panel to send incoming calls from your DIDWW numbers to Retell AI.
This trunk defines the SIP path that delivers calls to your Retell AI agent.

### Before You Begin

- An active DIDWW account is required. [Sign in to DIDWW](https://my.didww.com/users/sign_in) or [Create DIDWW account](https://my.didww.com/users/sign_up#/users/sign_up).
- At least one active **DID number** with capacity to receive incoming calls is required. [Buy Numbers](https://my.didww.com/users/sign_up#/coverage).

### Step 1: Create New SIP Trunk

1. In the [DIDWW User Panel](https://my.didww.com/#/trunks), go to **Voice > Inbound Trunks**.
2. Click **Create New > SIP Trunk**.

[![Creating a new inbound SIP trunk](../../_images/inbound11.png)](../../_images/inbound11.png)


Fig. 1. Creating a new inbound SIP trunk

### Step 2: Configure General SIP Trunk Settings

In the Create Inbound SIP Trunk form, enter the main requirements to route the calls to Retell AI.

1. In the **General** tab, enter a descriptive **Name** for the trunk (e.g., `Retell AI`).
2. Select **Static Endpoint**.
3. In **Host**, enter the Retell AI SIP endpoint hostname: `sip.retellai.com`.
4. In **Port**, enter the port that corresponds to the transport protocol:

   - `5060` for **TCP** or **UDP**
   - `5061` for **TLS**
5. In **Transport**, select **TCP**, **UDP**, or **TLS**.

[![SIP trunk configured for Retell AI](../../_images/generalsettings1.png)](../../_images/generalsettings1.png)


Fig. 2. SIP trunk configured for Retell AI

### Step 3: Click Create and Save Inbound SIP Trunk Configuration

When all required fields in the Create Inbound SIP Trunk are filled, click **Create** to save your inbound SIP trunk.

Note

For advanced SIP trunk configuration, see [Advanced Inbound SIP Trunk
documentation](../../voice/inbound-trunks/creating-a-new-sip-trunk.html#user-panel-sipin-trunk-advanced-configuration).

[![Create the Inbound SIP Trunk](../../_images/inbound2.png)](../../_images/inbound2.png)


Fig. 3. Create the Inbound SIP Trunk

### Step 4: Assign Inbound SIP Trunk to Your DID Numbers

After creating the Inbound SIP Trunk for Retell AI, assign it to the DID number(s) that will deliver incoming calls to
your Retell AI agent.

1. In the DIDWW User Panel, go to **Phone Numbers > My Numbers**.
2. Select the DID number(s) you want to assign to the inbound SIP trunk.
3. At the bottom of the page, click **Batch Actions > Update Trunks**.

[![Assigning a SIP trunk to DID numbers](../../_images/inbound3.png)](../../_images/inbound3.png)


Fig. 4. Selecting **Update Trunks** from the Batch Actions menu

4. From the dropdown menu, choose the **Retell AI SIP trunk** you created earlier.
5. Click **Confirm** to apply the changes.

[![Assigning a SIP trunk to DID numbers](../../_images/inbound41.png)](../../_images/inbound41.png)


Fig. 5. Assigning the newly created SIP trunk to the selected DID(s)



---

## 2. Enable Outbound Calling from Retell AI Through DIDWW

Configure an Outbound SIP Trunk in the DIDWW User Panel to allow Retell AI agents to place outbound calls through DIDWW.
This trunk provides the SIP credentials and routing settings required for outbound calls to external phone numbers.

### Before You Begin

Access to **DIDWW Outbound Trunks** is required for making outbound calls. See [Get Access to DIDWW Outbound
Termination](../../voice/outbound-trunks/get-access.html#user-panel-voice-out-get-access).

### Step 1: Create New Outbound Voice Trunk

1. In the [DIDWW User Panel](https://my.didww.com/#/trunks), go to **Voice > Outbound Trunks**.
2. Click **Create New**.

[![Creating a new outbound SIP trunk](../../_images/outbound11.png)](../../_images/outbound11.png)


Fig. 6. Creating a new outbound SIP trunk

### Step 2: Configure Authentication

1. Update the **Friendly Name** (e.g., `Retell AI`).
2. Keep the default **Credentials & IP-based** authentication method selected. The SIP digest credentials (username and password) will be provided after the trunk is created.
3. In **Allowed SIP IP addresses**, enter the public IP address subnet from which Retell AI will send outbound SIP traffic: `18.98.16.120/30`.

Note

Retell AI SIP traffic originates from IP ranges that may vary depending on your plan or region.
Refer to the official Retell AI documentation for the most up-to-date information:
[Retell AI SIP Trunking IP Information](https://docs.retellai.com/deploy/custom-telephony#overview)

Warning

You can allow all traffic by adding `0.0.0.0/0`, which removes all IP restrictions.
Although SIP Digest Authentication will still verify requests using valid credentials, this setup is not recommended.
Restrict access to known Retell AI IPs whenever possible.

[![Configuring allowed SIP IP addresses for outbound trunk authentication](../../_images/outbound2.png)](../../_images/outbound2.png)


Fig. 7. Entering allowed SIP IP addresses for outbound authentication

### Step 3: Click Create and Save Outbound SIP Trunk Configuration

When all required fields in the Create Outbound SIP Trunk are filled, click **Create** to save your outbound SIP trunk.

Note

For advanced outbound SIP trunk configuration, see [Outbound SIP Trunk
Guide](../../voice/outbound-trunks/how-to-guides/index.html#outbound-trunk-create).

[![Outbound SIP trunk created](../../_images/outbound31.png)](../../_images/outbound31.png)


Fig. 8. Outbound SIP trunk created and ready for use

### Step 4: View Outbound Trunk Credentials

After the outbound trunk is created, you can view its credentials by selecting the key icon in the Credentials column on
the Outbound Trunks page.

1. Go to **Voice > Outbound Trunks**.
2. Locate your outbound trunk and click the **key icon** in the **Credentials** column.
3. The trunk credentials will appear, showing the **Username** and **Password** (click the **eye icon** to reveal the password).
4. Copy and securely store these credentials. You will need them later when configuring Retell AI in [Step 2: Enter SIP Trunking Details](#retell-configure-number).

[![Accessing outbound trunk credentials](../../_images/outbound41.png)](../../_images/outbound41.png)


Fig. 9. Opening the outbound trunk credentials view



---

## 3. Connect DIDWW Numbers to Retell AI

To connect your **DIDWW phone numbers** with **Retell AI**, you'll configure the DIDWW SIP trunking details inside
Retell AI.
This setup imports your existing DID numbers and assigns an **AI agent** to handle both incoming and outgoing calls.

### Before You Begin

- A **Retell AI account** is required. [Sign in to Retell AI](https://www.retellai.com/) or create an account if needed.
- **AI Voice Agent** is required in Retell AI. See the [Retell AI Quickstart Guide](https://docs.retellai.com/get-started/quick-start) for guidance on creating an agent.

### Step 1: Open Phone Numbers Page

1. In the Retell AI dashboard, go to **Deploy > Phone Numbers**.
2. Click the **+** button and select **Connect to your number via SIP trunking**.

[![Opening SIP trunking connection in Retell AI](../../_images/retell1.png)](../../_images/retell1.png)


Fig. 10. Starting SIP trunking configuration in Retell AI

### Step 2: Enter SIP Trunking Details

In the SIP trunk configuration window, enter your DIDWW number and outbound routing details.

1. Enter your **Phone Number** in E.164 format without the `+` symbol (e.g., `18489005419`).
2. In **Termination URI**, enter the DIDWW [outbound signaling endpoint](../../voice/outbound-trunks/outbound-sip-information.html#voice-out-signaling-endpoints) (e.g., `out.didww.com`).
3. Enter the **SIP Trunk Username** and **SIP Trunk Password** from [Step 4: View Outbound Trunk Credentials](#retell-create-outbound-trunk-copy-credentials).
4. (Optional) Enter a **Nickname** to identify the number (e.g., `DIDWW Number`).
5. Select **Outbound Transport** (e.g., `TCP`).
6. Click **Save** to add your DIDWW number to Retell AI.

After saving, the number will appear in the **Phone Numbers** list.

[![Entering SIP trunk configuration details in Retell AI](../../_images/retell2.png)](../../_images/retell2.png)


Fig. 11. Configuring SIP trunk connection settings

### Step 3: Assign Call Agents

Configure which AI agents will handle inbound and outbound calls for your DIDWW number.

1. In the **Inbound Call Agent** section, select the **Call Agent** to handle incoming calls.
2. In the **Outbound Call Agent** section, select the **Call Agent** to use for outbound calls.
3. (Optional) Configure additional options such as allowed countries or webhook settings.

[![Configuring inbound and outbound call agents in Retell AI](../../_images/retell3.png)](../../_images/retell3.png)


Fig. 12. Assigning inbound and outbound AI agents

### Step 4: Test the Configuration

Verify that both inbound and outbound calling are working as expected.

1. Place a test call to your **DIDWW DID number** to confirm that inbound calls are routed to Retell AI and handled by the assigned **AI agent**.
2. In the Retell AI dashboard, use the **Make an outbound call** option to place a test call through your DIDWW outbound trunk.

Ensure that calls are successfully established in both directions and that the correct agents are handling the
interactions.

Note

You can review call activity and verify call status or error codes in the DIDWW **Inbound** and **Outbound Call Logs**.
See [Inbound Call Logs](../../logs-analytics/call-logs/inbound-logs.html#inbound-cdr-logs) and [Outbound Call
Logs](../../logs-analytics/call-logs/outbound-logs.html#outbound-cdr-logs) for more details.

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