Introduction to Amazon VPC

Introduction

Amazon Virtual Private Cloud (Amazon VPC) is arguably the most important, yet most complex, foundational service in AWS.

A VPC is a logically isolated section of the AWS Cloud where you can launch AWS resources in a virtual network that you define. You have complete control over your virtual networking environment, including selection of your own IP address range, creation of subnets, and configuration of route tables and network gateways.

The Default VPC

When you create a new AWS account, AWS automatically creates a "Default VPC" in every Region. When you launch an EC2 instance without specifying a network, it launches into this Default VPC, assigns itself a public IP address, and is instantly accessible from the internet.

While this is great for learning, the Default VPC is generally considered insecure for production workloads because everything is public by default.

Custom VPC Architecture

For production, you design a Custom VPC with a clear separation between public and private resources.

1. Public Subnets

A Subnet is a subdivision of your VPC's IP address range. Resources in a Public Subnet have a route to the Internet Gateway, meaning they can be accessed from the public internet.

• Use cases: Public-facing load balancers, Bastion Hosts (Jump Boxes), NAT Gateways.

2. Private Subnets

Resources in a Private Subnet do not have a direct route to the Internet Gateway. They are completely hidden from the public internet.

• Use cases: Application servers, EC2 instances, RDS databases.

If a hacker scans the internet, they cannot even see the IP addresses of your backend servers or databases because they exist solely within the private internal network of your VPC!

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