Adding a SNAT Rule to a Public NAT Gateway to Enable Servers to Share an EIP to Access the Internet

Scenarios

If servers without EIPs need to access the Internet, they can share an EIP to access the Internet through a public NAT gateway. This helps save EIP resources and protect servers from exposing their IP addresses.

Operation Process

Preparations

Before using NAT gateways, you need to:

• Create a HUAWEI ID and enable Huawei Cloud services.
• Complete real-name authentication.
• Top up your account.

Step 1: Assign an EIP

1. Go to the Buy EIP page.
2. On the Buy EIP page, set the EIP name to EIP-A.

   You can configure other EIP parameters as required. For details, see Assigning an EIP.

3. Click Next.

   Return to the EIP list to view EIP-A you have assigned.

Step 2: Create a Public NAT Gateway

1. Go to the Buy Public NAT Gateway page.
2. On the Buy Public NAT Gateway page, configure required parameters.

   Table 1 Parameters for creating a public NAT gateway

   Parameter	Example	Description
   Region	CN North-Beijing4	The region where the public NAT gateway is located.
   Billing Mode	Pay-per-use	The billing mode of the public NAT gateway.
   Specifications	Small	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.
   Name	public-nat-01	The name of the public NAT gateway. Enter up to 64 characters. Only letters, digits, underscores (_), hyphens (-), and periods (.) are allowed.
   VPC	VPC-A	The VPC that the public NAT gateway belongs to. The VPC cannot be changed after the public NAT gateway is created. NOTE: To allow traffic to pass through the public NAT gateway, a route pointing to the public NAT gateway in the VPC route table is required. When you create a public NAT gateway, a default route with the destination of 0.0.0.0/0 pointing to the public NAT gateway is automatically added to the default route table of the VPC. If the route table already has a route with the destination of 0.0.0.0/0, the default route that points to the public NAT gateway will fail to be added. In this case, manually add a route that points to the gateway or create a custom route table and add a route with the destination of 0.0.0.0/0 pointing to the gateway to the new route table.
   Subnet	Subnet-A01	The subnet that the public NAT gateway belongs to. The subnet must have at least one available IP address. The subnet cannot be changed once the public NAT gateway is created. The NAT gateway will be deployed in the selected subnet and work for the entire VPC where it is deployed. To enable communications over the Internet, add SNAT or DNAT rules.
   Enterprise Project	default	The enterprise project that the public NAT gateway belongs to. If you do not specify an enterprise project, the default enterprise project will be used. You can configure an enterprise project for a public NAT gateway only after the enterprise project function is enabled.
   Advanced Settings (Optional)	-	Click the drop-down arrow to configure advanced parameters of the public NAT gateway.
   SNAT Connection TCP Timeout (s)	900	The timeout period of a TCP connection established using the SNAT rule. If no data is exchanged within this period, the TCP connection will be closed. Value range: 40 to 7200
   SNAT Connection UDP Timeout (s)	300	The timeout period of a UDP connection established using the SNAT rule. If no data is exchanged within this period, the UDP connection will be closed. Value range: 40 to 7200
   SNAT Connection ICMP Timeout (s)	10	The timeout period of an ICMP connection established using the SNAT rule. If no data is exchanged within this period, the ICMP connection will be closed. Value range: 10 to 7200
   TCP TIME_WAIT (s)	5	How long the side that actively closed the TCP connection is in the TIME_WAIT state. Value range: 0 to 1800
   Description	Not required	Supplementary information about the public NAT gateway. Enter up to 255 characters. Angle brackets (<>) are not allowed.
   Tag	Not required	The identifier of the public NAT gateway. A tag is a key-value pair. You can add up to 20 tags to each NAT gateway.

3. Click Next. On the page displayed, confirm the public NAT gateway specifications.
4. Click Submit.

   On the Public NAT Gateways page, you can view the purchased public NAT gateway in the list.

Step 3: Add an SNAT Rule

1. Go to the public NAT gateway list page.
2. On the public NAT gateway list page, click the name of the public NAT gateway on which you need to add an SNAT rule.
3. On the SNAT Rules tab, click Add SNAT Rule.
4. Configure required parameters. Table 2 describes the parameters.

   Table 2 Descriptions of SNAT rule parameters

   Parameter	Example	Description
   Scenario	VPC	The scenario where the SNAT rule is used. Select VPC if your servers in a VPC need to access the Internet. Select Direct Connect/Cloud Connect if servers in your on-premises data center or in another VPC need to access the Internet.
   CIDR Block	Existing	In the VPC scenario, specify a VPC subnet CIDR block to enable servers in that subnet to access the Internet using the SNAT rule. In the Direct Connect/Cloud Connect scenario, specify a CIDR block of your data center or your VPC to enable your servers to access the Internet using the SNAT rule.
   Public IP Address Type	EIP	The EIP used for accessing the Internet.
   Monitoring	-	You can create alarm rules on the Cloud Eye console to monitor your SNAT connections and keep informed of any changes in a timely manner.
   Description	Not required	Supplementary information about the SNAT rule. Enter up to 255 characters. Angle brackets (<>) are not allowed.

5. Click OK.

Step 4: Verify that the SNAT Rule Has Been Added

In the SNAT Rules tab, view details of the SNAT rule.

If the rule status is Running, the SNAT rule is created.

Figure 1 Verifying that the SNAT rule has been added

Step 5: Verify Whether the Server Can Access the Internet Through the NAT Gateway

1. Go to the ECS list page.
2. Log in to the server to be verified.
3. Verify that the server can access the Internet.
   Figure 2 Verification result