What Are the Relationships and Differences Between the CIDR Blocks in a NAT Gateway and in an SNAT Rule?

When creating a NAT gateway, you must specify the VPC and subnet CIDR block for the NAT gateway. This CIDR block can only be used by the system.

When you are creating an SNAT rule and set Scenario to VPC, select a subnet in the target VPC. This way, servers in the subnet can access the Internet through the SNAT rule.

When you are creating an SNAT rule and set Scenario to Direct Connect, enter a CIDR block of an on-premises data center or another VPC. With this, on-premises servers or cloud servers in the CIDR block can access the Internet through the SNAT rule.