# NAT Gateways

## Introduction

A network address translation (NAT) gateway enables instances in a private
subnet to connect to the internet via an elastic IP address, as shown in the
diagram below:

![image3](media/02-NAT-Gateway-Overview_Symphony-1024x797.png)

See the video introducing Internet Gateways and NAT Gateways:

<iframe class="embed-responsive-item"
        id="youtubeplayer"
        type="text/html"
        width="640"
        height="390"
        style="border: none"
        src="//www.youtube.com/embed/BRNBmwjslRQ"
        allowfullscreen="allowfullscreen">
</iframe>

## Creating a NAT Gateway

**To create a NAT Gateway:**

1. Navigate to the **Networking > NAT Gateways** view.
2. From the top toolbar, click **Create**.
3. In the **Create NAT Gateway** dialog, enter the following:
   * **Name** - name of the NAT gateway.
   * **Description** - optional description of the NAT gateway.
   * **VPC** - VPC which is associated with this route table.
   * **Subnet** - select subnet in which the NAT gateway will reside.
   * **Elastic IP** - select elastic IP for NAT gateway.
4. Click **OK**.
5. After creation of the NAT gateway, update the route table associated with
   at least one of your private subnets such that Internet-bound traffic
   is directed towards the NAT gateway.
6. The instances in your private subnets will now be able to communicate with
   the internet.

## Sample NAT Gateway Configuration Flow

The following procedure provides a complete end-to-end configuration example
including VPC and route table configurations related to NAT gateways.

1. To create a VPC with a NAT Gateway, navigate to the **Networking** > **VPCs**
   view, and click **Create**.
2. In the **Create VPC** window, select an existing Internet Gateway from the
   pull-down list or create a new one by clicking **+**.
3. Create two subnets in the VPC, one called Public and the other called Private.
   1. Navigate to the **Networking** > **Subnets** view and click **Create**.
   2. In the **Create Subnet** window, create a subnet called ‘public’.
   3. Click **OK**.
   4. Click **Create** again.

      ![image5](media/05-Create-Subnet.png)
   5. In the **Create Subnet** window, create a subnet called ‘private’.
   6. Click **OK**.
4. Create two route tables in the VPC, one called public and the other called private.
   1. Navigate to the **Networking** > **Route Tables** view and click **Create**.
   2. In the **Create Route Table** window, create a Route Table called ‘public’.
   3. Click **OK**.
   4. Click **Create** again.
   5. In the **Create Route Table** window, create a Route Table called ‘private’.
   6. Click **OK**.
5. Associate the public subnet to the public route table, and the private
   subnet to the private route table.
   1. Navigate to the **Networking** > **Route Tables** view and click on the
      **public** route table.
   2. In the bottom of the display showing the Route Table details, select the
      **Subnet Associations** tab.
   3. Click **Associate**.

      ![image6](media/06-associate-public-subnet.png)
   4. In the Associate Subnet window, associate the **public** subnet to the
      **public** route table.
   5. Click **OK**.
   6. Navigate to the **Networking** > **Route Tables** view and click on the
      **private** route table.
   7. In the bottom of the display showing the Route Table details, select the
      **Subnet Associations** tab.
   8. Click **Associate**.

      ![image7](media/07-associate-private-subnet.png)
   9. In the Associate Subnet window, associate the **private** subnet to the
      **private** route table.
   10. Click **OK**.
6. In the **public** route table create a default route with the VPC Internet
   Gateway as the target.
   1. Navigate to the **Networking** > **Route Tables** view and click on the
      **public** route table.
   2. In the bottom of the display showing the Route Table details, select the
      **Routes** tab.
   3. Click **Create**.
   4. In the **Create Route** window, create a default route (0.0.0.0/0) with
      the VPC Internet Gateway as the target.
   5. Click **OK**.

      ![image8](media/08-create-default-route-gtwy.png)
      </p>
7. Create a NAT gateway on the public subnet and allocate an elastic IP to it.
   Wait for the NAT GW state to move from pending to available.
   </p>
   1. Navigate to the **Networking** > **NAT Gateways** view and click **Create**.
   2. In the **Create NAT Gateway dialog** window, select an existing elastic
      IP from the drop down list or click **+** to create a new one.

      ![image9](media/09-create-nat-gateway.png)
   3. Click **OK**.
8. In the **private** route table create a default route with the created
   NAT Gateway as the target.
   1. Navigate to the **Networking** > **Route Tables** view and click on the
      **private** route table.
   2. In the bottom of the display showing the Route Table details, select the
      **Routes** tab.
   3. Click **Create**.
   4. In the **Create Route** window, create a default route (0.0.0.0/0) with
      the created NAT Gateway as the target.

      ![image10](media/10-private-route-nat-gateway.png)
      </p>
   5. Click **OK**.
9. Create a VM on the private subnet
   1. Navigate to the **Compute** > **Instances** and click **Create**.

      ![image11](media/11-create-vm-private-subnet.png)
   2. In the **Create VM wizard**, associate the VM with the private subnet
      created.
10. You can now connect the VM to the internet via the NAT Gateway Elastic IP.
11. View the Network Topology diagram of the NAT Gateway in a VPC.
    1. In the **Networking** > **Overview** screen see the VPC view
       of the Network Topology.

       ![image13](media/13-network-overview.png)

       **Note:** The red Subnet and VPC frames and labels shown in the diagram
       are illustrative only and not part of the Zadara Cloud Services Network
       Topology UI display.