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

# Aviatrix Gateway to Aviatrix Gateway

> This section describes how to configure an IPsec tunnel between an Aviatrix Gateway and another Aviatrix Gateway using Aviatrix Site2Cloud.

This section describes how to configure an IPsec tunnel between an Aviatrix
Gateway and another Aviatrix Gateway using Aviatrix Site2Cloud.

<Note>
  There are only a couple of reasons to use Site2Cloud when connecting two Aviatrix Gateways:

  1. You have overlapping CIDR blocks but need to peer two VPC/VNets.
  2. The two Aviatrix Gateways are not part of the same Controller (i.e., one is
     at your customer and the other one is in your environment).
</Note>

## Deployment

There are two Aviatrix Gateways in this scenario. Since you are using the
Site2Cloud feature, you must configure each side of the tunnel individually.

In this procedure the gateways are referred to as **Gateway A** and **Gateway
B**. You can pick either gateway to be **Gateway A** or **Gateway B**.

### Configure Tunnel from Gateway A to Gateway B

1. Follow the steps in
   <a href={"/docs/enterprise/" + "10.1" + "/guides/connectivity/vpn/s2c-configuration-workflow"}>Site2Cloud Configuration Workflow</a>
   to create a Mapped or Unmapped external (Site2Cloud) connection. Use this
   table for specific field values.

| Field                   | Description                                                     |
| ----------------------- | --------------------------------------------------------------- |
| Connect Public Cloud to | External Device: Static Route-Based/Static Route-Based (Mapped) |
| Local Gateway           | Select **Gateway A** from the dropdown.                         |
| Remote Device Type      | Aviatrix                                                        |
| Remote Device IP        | Enter the public IP address of **Gateway B**.                   |
| Pre-shared Key          | Leave blank and Aviatrix will generate                          |

2. Click **Save**.
3. Once complete, click the vertical ellipsis <img src={"/docs/enterprise/" +
   "10.1" + "/guides/connectivity/vpn/images/threedot.png"} alt="25" style={{display: 'inline', verticalAlign: 'middle', height: '1em'}} /> menu
   next to the new external connection and select **Download Configuration**.
4. Select **Aviatrix** for Vendor, **UCC** for Platform and **1.0** for
   Software.
5. Click **Download**. You can use the information in this file to create the
   other side of the tunnel.

### Configure Tunnel from Gateway B to Gateway A

1. Go to Networking > Connectivity > External Connections (S2C).
2. Create a new external connection using the information from the downloaded
   configuration file. Use this table for specific values:

| Field                   | Description                                                      |
| ----------------------- | ---------------------------------------------------------------- |
| Connect Public Cloud to | External Device: Static Route-Based/Static Route-Based (Mapped). |
| Local Gateway           | Select **Gateway B** from the dropdown.                          |
| Remote Device Type      | Aviatrix                                                         |
| Remote Device IP        | Enter the public IP address of **Gateway A**.                    |
| Pre-shared Key          | Leave blank and Aviatrix will generate                           |

3. Click **Save**.

## Test

Once complete, you can check tunnel status at Diagnostics > Cloud Routes >
External Connections.

## Troubleshoot

Wait 2-3 minutes for the tunnel to come up. If it does not come up within that
time, check the IP addresses to confirm they are accurate. Additional
troubleshooting is available at Diagnostics > Diagnostic Tools.

## Related Topics

* [About External Connection Settings](https://legacy.docs.aviatrix.com/documentation/latest/network/externaldevice-settings.html)