Help Center/ NAT Gateway/ User Guide/ Public NAT Gateways/ Managing SNAT Rules/ Adding an SNAT Rule
Updated on 2024-08-13 GMT+08:00
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Adding an SNAT Rule

Scenarios

After a public NAT gateway is created, add an SNAT rule, so that servers in a VPC subnet or servers that are connected to a VPC through Direct Connect or Cloud Connect can access the Internet by sharing an EIP.

One SNAT rule takes effect for only one subnet. If there are multiple subnets in a VPC, create multiple SNAT rules to allow servers in them to share EIPs.

Constraints and Limitations

  • Only one SNAT rule can be added for each VPC subnet.
  • When you add an SNAT rule in the VPC scenario, the custom CIDR block must be a subset of the NAT gateway's VPC subnets.
  • If an SNAT rule is used in the Direct Connect scenario, the custom CIDR block must be a CIDR block of a Direct Connect connection and cannot overlap with the NAT gateway's VPC subnets.
  • There is no limit on the number of SNAT rules that can be added on a public NAT gateway.

Prerequisites

A public NAT gateway is available.

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 the name of the public NAT gateway on which you need to add an SNAT rule.
  5. On the SNAT Rules tab, click Add SNAT Rule.
    Figure 1 Add SNAT Rule
  6. Configure required parameters. For details, see Table 1.
    Table 1 Descriptions of SNAT rule parameters

    Parameter

    Description

    Scenario

    The scenarios 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.

    Subnet
    • Existing: Select an existing subnet.
    • Custom: Customize a CIDR block or enter a server IP address.
      NOTE:

      When you select Custom, you can enter 0.0.0.0/0.

      Only a 32-bit server IP address is supported.

    Public IP Address Type

    The EIP used for accessing the Internet

    You can select an EIP that either has not been bound, has been bound to a DNAT rule of the current public NAT gateway with Port Type set to Specific port, or has been bound to an SNAT rule of the current public NAT gateway.

    You can select up to 20 EIPs for an SNAT rule. If you have selected multiple EIPs for an SNAT rule, one EIP will be chosen randomly.

    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

    Provides supplementary information about the SNAT rule. Enter up to 255 characters. Angle brackets (<>) are not allowed.
  7. Click OK.
    • You can add multiple SNAT rules for a public NAT gateway to suite your service requirements.
    • Each VPC can be associated with multiple public NAT gateways.
    • Only one SNAT rule can be added for each VPC subnet.
Parent topic: Managing SNAT Rules