nat
The NAT CIDR block to be created. The CIDR block must meet the following conditions: It must be 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16, or one of their subnets. The subnet mask must be 16 to 32 bits in lengths. To use a public CIDR block as the NAT CIDR block, the VPC to which the VPC NAT gateway belongs must be authorized to use public CIDR blocks. For more information, see Create a VPC NAT gateway.