NAT Gateway is an enterprise-class Internet gateway that provides NAT proxy services (SNAT and DNAT), with the forwarding capacity of up to 10 Gbps, and the capability of cross-zone disaster recovery. The position of NAT Gateway in the VPC network topology is as shown in the following figure.

As an Internet gateway, NAT Gateway needs to be configured with a public IP to function normally. After creating a NAT gateway, you can bind an EIP to it.
Note  If your account has a NAT bandwidth package before January 26, 2018, you still need to use the bandwidth package to provide public IPs. Open a ticket if you want to bind EIP to the NAT gateway.