NAT Gateway

IGW is used to direct the traffic to the open internet and is associated with the Route Table intended for public subnets. This means the connection to a particular instance can be initiated from the open internet and from the instance itself. For a private subnet, you cannot initiate the connection from the open internet. But for software patches downloads, or to interact with other AWS services, you need to have a route to the internet so that the connection initiated from the instance should be able to download the patches or work with other AWS services; but no one should be able to initiate the connection from the open internet. This is where we need the NAT Gateway.

The NAT Gateway enables instances in a private subnet to connect to the open internet or to other AWS services, but it prevents the open internet from initiating the connection to those private instances. The NAT Gateway is highly available and fully managed by AWS. It has the capability to burst up to 10 Gbps...