A NAT can be defined as a virtual router or a gateway in a VPC, which enables instances in a private subnet to interact with the internet. It's an important stopping point for data on its way from private subnets to the internet without directly exposing the instances to the internet. It acts as a firewall, dynamically assigns a temporary public address to an instance, and routes the traffic between the requesting instances and the internet.
There are two types of NAT devices:
- NAT gateway: This is the gateway service provided and managed by AWS
- NAT instance: This is a custom-provisioned EC2 instance hosting NAT services
These NAT devices only support IPv4 network traffic. EC2 instances in a private subnet do not have a public or an Elastic IP and a subnet's route table does not have route entry to send traffic directly to the internet through an IGW. The NAT device acts as an intermediate point between instances and IGWs. It receives traffic from an EC2 instance residing in a private subnet...