Creating a Public NAT Gateway

Scenarios

Create a public NAT gateway to enable your servers to access the Internet or provide services accessible from the Internet.

Constraints and Limitations

• Rules on one public NAT gateway can use the same EIP, but rules on different NAT gateways must use different EIPs.
• Each VPC can be associated with multiple public NAT gateways.
• SNAT and DNAT rules can use the same EIP to save resources. However, an SNAT rule cannot share an EIP with a DNAT rule whose Port Type is set to All ports, because the resource in the DNAT rule will preferentially use all ports of the EIP.
• The public NAT gateway does not translate IP addresses for Enterprise Edition VPN.
• If both an EIP and a public NAT gateway are configured for a server, data will be forwarded through the EIP.
• Private IP addresses used by load balancers cannot be selected when you add DNAT rules on public NAT gateways for Internet communications.
• After you perform operations on backend resources, such as changing the specifications of an ECS, the existing NAT gateway rules will become invalid. Delete the rules and create some new rules for the ECS of the new specifications.
• Some carriers will block the following ports for security reasons. It is recommended that you do not use the following ports.

  Protocol	Port
  TCP	42 135 137 138 139 444 445 593 1025 1068 1434 3127 3128 3129 3130 4444 4789 4790 5554 5800 5900 9996
  UDP	135~139 1026 1027 1028 1068 1433 1434 4789 4790 5554 9996

Prerequisites

• The VPC and subnet where your public NAT gateway will be deployed are available.
• To allow traffic to pass through the public NAT gateway, a route to the public NAT gateway in the VPC is required. When you buy a public NAT gateway, a default route 0.0.0.0/0 to the public NAT gateway is automatically added to the default route table of the VPC. If the default route 0.0.0.0/0 already exists in the default route table of the VPC before you buy the public NAT gateway, the default route that points to the public NAT gateway will fail to be added automatically. In this case, perform the following operations after the public NAT gateway is successfully created: Manually add a different route that points to the gateway or create a default route 0.0.0.0/0 pointing to the gateway in the new routing table.

Procedure

1. Log in to the management console.
2. Click in the upper left corner and select the desired region and project.
3. Click Service List in the upper left corner. Under Networking, select NAT Gateway.

   The Public NAT Gateway page is displayed.

4. On the displayed page, click Buy Public NAT Gateway.
5. Configure required parameters. For details, see Table 1.

   Table 1 Descriptions of public NAT gateway parameters

   Parameter	Description
   Region	The region where the public NAT gateway is located
   Name	The name of the public NAT gateway Enter up to 64 characters. Only digits, letters, underscores (_), and hyphens (-) are allowed.
   VPC	The VPC that the public NAT gateway belongs to The selected VPC cannot be changed after you buy the public NAT gateway. NOTE: To allow traffic to pass through the public NAT gateway, a route to the public NAT gateway in the VPC is required. When you buy a public NAT gateway, a default route 0.0.0.0/0 to the public NAT gateway is automatically added to the default route table of the VPC. If the default route 0.0.0.0/0 already exists in the default route table of the VPC before you buy the public NAT gateway, the default route that points to the public NAT gateway will fail to be added automatically. In this case, perform the following operations after the public NAT gateway is successfully created: Manually add a different route that points to the gateway or create a default route 0.0.0.0/0 pointing to the gateway in the new routing table.
   Subnet	The subnet that the public NAT gateway belongs to The subnet must have at least one available IP address. The selected subnet cannot be changed after you buy the public NAT gateway. The NAT gateway will be deployed in the selected subnet. The NAT gateway works for the entire VPC where it is deployed. To enable communications over the Internet, add SNAT or DNAT rules.
   Specifications	The specifications of the public NAT gateway The value can be Extra-large, Large, Medium, or Small. To view more details about specifications, click Learn more on the page.
   Enterprise Project	The enterprise project that the public NAT gateway belongs to If an enterprise project has been configured, select the enterprise project. If you have not configured any enterprise project, select the default enterprise project.
   Description	Supplementary information about the public NAT gateway Enter up to 255 characters.
   Tag	The public NAT gateway tag. A tag is a key-value pair. You can add up to 10 tags to each public NAT gateway. The tag key and value must meet the requirements listed in Table 2.

   Table 2 Tag requirements

   Parameter	Requirement
   Key	Cannot be left blank. Must be unique for each NAT gateway. Can contain a maximum of 36 characters. Cannot contain equal signs (=), asterisks (*), left angle brackets (<), right angle brackets (>), backslashes (\), commas (,), vertical bars (|), and slashes (/), and the first and last characters cannot be spaces.
   Value	Can contain a maximum of 43 characters. Cannot contain equal signs (=), asterisks (*), left angle brackets (<), right angle brackets (>), backslashes (\), commas (,), vertical bars (|), and slashes (/), and the first and last characters cannot be spaces.

6. Click Create Now. On the page displayed, confirm the public NAT gateway specifications.
7. Click Submit to create a public NAT gateway.

   It takes 1 to 6 minutes to create a public NAT gateway.

8. In the list, view the status of the public NAT gateway.

Adding a Default Route Pointing to the Public NAT Gateway

1. Log in to the management console.
2. Click in the upper left corner and select the desired region and project.
3. Under Networking, select Virtual Private Cloud.
4. In the navigation pane on the left, choose Route Tables.
5. On the Route Tables page, click Create Route Table in the upper right corner.

   VPC: Select the VPC to which the public NAT gateway belongs.

6. After the custom route table is created, click its name.

   The Summary page is displayed.

7. Click Add Route and configure parameters as follows:

   Destination: Set it to 0.0.0.0/0.

   Next Hop Type: Select NAT gateway.

   Next Hop: Select the created NAT gateway.

8. Click OK.