> For a complete page index, fetch https://docs.synthflow.ai/llms.txt. For full documentation content, fetch https://docs.synthflow.ai/llms-full.txt.

# Vonage

> Connect Vonage to Synthflow via SIP trunking so Vonage-based call flows can use AI agents.

A Vonage SIP trunk connects your Vonage numbers to Synthflow, so agents place and receive calls on them. You create the trunk in the Vonage API dashboard, then import each number into Synthflow.

> **Note**
>
> Vonage does not support SIP REFER, so cold transfers do not work on Vonage SIP trunks. Use [warm transfers](/call-transfers#transfer-modes) only. See [Vonage's documentation](https://api.support.vonage.com/hc/en-us/articles/360039121391-Is-SIP-REFER-supported).

## Vonage SIP trunk

**New trunk.** In the Vonage API dashboard, open **Voice** → **SIP**, then select **+ Create New**.

![Vonage API dashboard showing the SIP trunks list and the Create New button](https://storage.googleapis.com/granular-changelog/doc-images/vonage-sip-trunks-dashboard.png)

**Domain name.** Enter a domain name for the trunk. It must be 5 to 32 characters, using only letters, digits, and dashes.

![Vonage Create SIP trunk form with the domain name field](https://storage.googleapis.com/granular-changelog/doc-images/vonage-create-sip-trunk.png)

**Authentication.** In the trunk's **Authentication** section, turn on **User Key and Secret**, **Access Control List (ACL)**, or both. At least one is required.

For user key and secret:

* The **User Key** is the username you enter when you import the number into Synthflow.
* The **Secret** is the password. It must be 12 to 64 characters, with at least one digit, one lowercase letter, and one uppercase letter. Use a unique, generated password.

![Vonage trunk Authentication section with User Key and Secret fields](https://storage.googleapis.com/granular-changelog/doc-images/vonage-authentication.png)

Once authentication is on, Vonage shows three regional termination URIs. Note the one for your region. You enter it, with the user key and secret, when you import the number.

| Vonage region                          | Termination URI                |
| -------------------------------------- | ------------------------------ |
| AMER (North and South America)         | `yourdomain.sip-us.vonage.com` |
| EMEA (Europe, Middle East, and Africa) | `yourdomain.sip-eu.vonage.com` |
| APAC (Asia Pacific)                    | `yourdomain.sip-ap.vonage.com` |

**Inbound and outbound settings.**

* **Inbound:** select the region that handles inbound PSTN calls to the trunk's numbers, for example **North America - East (api-us-3.vonage.com)**.
* **Outbound:** select **Add Authentication** and add a user key and secret, or an ACL.

![Vonage trunk inbound region and outbound authentication settings](https://storage.googleapis.com/granular-changelog/doc-images/vonage-inbound-outbound-config.png)

**Synthflow URI and numbers.** In **Add URI**, add Synthflow's SIP server:

* **Priority:** `1`
* **URI:** `sip.synthflow.ai:32681`. For US or EU workspaces, use your region's [SIP address](/connect-over-sip#sip-addresses) instead.
* **Transport:** UDP. You can leave SRTP unchecked.

In **Link numbers**, filter by country, features, or type, and select **Link** for each number to route through the trunk.

![Vonage trunk Add URI and Link numbers sections](https://storage.googleapis.com/granular-changelog/doc-images/vonage-add-uri-link-numbers.png)

## Number import

Import each number into Synthflow as a [custom number](/phone-numbers#adding-custom-numbers), so Synthflow knows how to route its calls. In the import form:

1. Select **Custom** as the number type.
2. Enter the number you linked to the trunk in Vonage.
3. In **SIP Domain**, enter the termination URI for your region, for example `yourdomain.sip-us.vonage.com`.
4. Enter the user key and secret as the username and password.
5. Optionally, add a friendly name for the trunk.

![Synthflow import phone number form filled in with Vonage SIP trunk details](https://storage.googleapis.com/granular-changelog/doc-images/vonage-import-phone-number.png)

The imported number places and receives calls like a number bought in Synthflow. To stop using it, delete it from **Phone Numbers**, or with the [Delete a phone number](/api-reference/platform-api/phone-numbers/delete-phone-number) API.

> Route Vonage numbers to Synthflow agents over a Vonage SIP trunk.