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

# SIP for Vapi

> Create a Free Vapi SIP trunk, copy SIP URI and digest credentials, link your assistant, paste into Tuner.

<Info>
  Start at [**Simulation SIP setup**](/docs/simulation/setup).
</Info>

## Step 1: Create a Free Vapi SIP trunk

1. Open the [Vapi dashboard](https://dashboard.vapi.ai/) → **Phone Numbers**.
2. **Create Phone Number** → **Free Vapi SIP**.
3. Fill in:
   * **SIP Identifier** (used in your SIP URI)
   * **Label** (your reference only)
   * **Username** and **Password** (digest auth)
4. Click **Import SIP URI**.

<img src="https://mintcdn.com/tuner/ymjXbsRhUG5GDj0_/images/simulation/vapi-create-sip-trunk.png?fit=max&auto=format&n=ymjXbsRhUG5GDj0_&q=85&s=d21464ed501b58a00a3999d5c0583ba5" alt="Creating a Free Vapi SIP trunk (Phone Numbers → Free Vapi SIP)" width="1024" height="649" data-path="images/simulation/vapi-create-sip-trunk.png" />

Your SIP URI will match:

```text theme={null}
sip:<SIP Identifier>@sip.vapi.ai
```

<Warning>
  **Save username and password immediately.** Vapi shows the password only once. If you lose it, delete the trunk and create a new one.
</Warning>

## Step 2: Link your assistant (required)

Simulation calls will **not** connect if this step is skipped.

1. **Phone Numbers** → click your SIP trunk.
2. Under **Inbound Settings**, set **Assistant** to the assistant Tuner should reach.
3. **Save**.

<img src="https://mintcdn.com/tuner/ymjXbsRhUG5GDj0_/images/simulation/vapi-link-assistant.png?fit=max&auto=format&n=ymjXbsRhUG5GDj0_&q=85&s=16f16587ea8987d12934cce38593935e" alt="Link your Vapi assistant to the SIP trunk — Inbound Settings" width="1024" height="633" data-path="images/simulation/vapi-link-assistant.png" />

## Step 3: Paste into Tuner

1. **Agent Settings** → **SIP Settings**.
2. **SIP URI:** `sip:<identifier>@sip.vapi.ai`
3. **Username** / **Password:** same values as in Step 1.

<img src="https://mintcdn.com/tuner/ymjXbsRhUG5GDj0_/images/simulation/sip-settings.png?fit=max&auto=format&n=ymjXbsRhUG5GDj0_&q=85&s=2a1b0de8f19925d16279808972da8c3a" alt="SIP configuration in Tuner" width="1024" height="303" data-path="images/simulation/sip-settings.png" />

## Troubleshooting

| Issue                 | What to check                                                                                                   |
| --------------------- | --------------------------------------------------------------------------------------------------------------- |
| Calls fail to connect | Assistant linked to trunk (Step 2). Credentials match Vapi and Tuner. URI exactly `sip:identifier@sip.vapi.ai`. |
| Assistant silent      | Assistant has a prompt and is active (not draft/paused).                                                        |
| Unverified in Tuner   | No trailing spaces on URI or password. **Verify & Save** again.                                                 |

Paste your SIP URI and credentials into **Agent Settings → SIP Settings**, click **Verify & Save**, and you're ready to run simulations.

***

<Card title="Run your first simulation" icon="flask" iconType="solid" href="/user-guide/simulation/introduction-to-call-simulation#how-it-works">
  Configure your simulation mix and start a batch.
</Card>