Why Do I Need DNAT?

In a public NAT gateway, DNAT enables servers in a VPC, regardless of if they are in the same AZ, to share an EIP to provide services accessible from the Internet. With an EIP, a public NAT gateway forwards the Internet requests from only a specific port and over a specific protocol to a specific port of a server, or it can forward all requests to the server regardless of which port they originated on. For details, see Adding a DNAT Rule.

In a private NAT gateway, DNAT enables servers, regardless of if they are in the same AZ, to share the same transit IP address to provide services accessible from on-premises data centers or other VPCs. For details, see Adding a DNAT Rule.