Internet Gateway

1.3 Summarize cloud concepts and connectivity options

📘CompTIA Network+ (N10-009)

Introduction to Cloud Gateways

In cloud networking, a gateway acts as a bridge that connects different networks or environments. It manages communication between your cloud resources (like virtual machines or subnets in a Virtual Private Cloud – VPC) and external networks, such as the public internet or on-premises data centers.

One of the most important types of cloud gateways is the Internet Gateway.

What is an Internet Gateway?

An Internet Gateway (IGW) is a cloud networking component that allows resources in a virtual network (such as a Virtual Private Cloud – VPC) to communicate with the internet.

It serves two main functions:

Outbound traffic – Allows instances (such as virtual machines or containers) inside the VPC to send data to the internet.
Inbound traffic – Allows resources on the internet to access resources in the VPC, if permitted by security rules.

Without an Internet Gateway, virtual machines or cloud resources would be isolated and unable to reach the internet for updates, communication, or remote access.

How the Internet Gateway Works

An Internet Gateway connects a VPC (Virtual Private Cloud) to the internet through a combination of:

Public IP addresses (assigned to instances)
Routing tables
Security controls (like firewalls or security groups)

Let’s break down how it works step-by-step:

1. Association with the VPC

The Internet Gateway is attached to a specific Virtual Private Cloud (VPC).
Each VPC can have only one Internet Gateway attached at a time.

2. Route Table Configuration

To enable internet access, the route table of the VPC must include a default route (0.0.0.0/0) that points to the Internet Gateway.
This tells the VPC to forward any traffic destined for external networks to the Internet Gateway.

3. Public IP Requirement

Instances that need direct internet access must have a public IP address or an Elastic IP address assigned.
This is how the Internet Gateway knows how to route traffic from the internet back to the correct instance.

4. Security Controls

Even with an Internet Gateway, communication is only possible if security groups and network ACLs (Access Control Lists) allow the required inbound and outbound traffic.
These act as firewalls to control what traffic can pass through.

Key Functions of an Internet Gateway

Function	Description
Outbound Connectivity	Allows instances to initiate connections to the internet (e.g., to download software or updates).
Inbound Connectivity	Enables external systems (like administrators or web users) to connect to the VPC’s resources if allowed.
Routing Management	Provides a target for internet-bound traffic in the route table.
Network Translation	Works with public IPs to translate private VPC addresses into public ones for internet communication.

Important Points to Remember for the Exam

One Internet Gateway per VPC – You can only attach one IGW to a single VPC at a time.
Stateless Component – Internet Gateways are not stateful devices. The stateful control (tracking inbound/outbound connections) is handled by security groups or firewalls.
Public IPs are Needed – Instances require public or elastic IPs to be reachable from the internet.
Route Table Configuration is Crucial – You must add a route (0.0.0.0/0) that points to the IGW for outbound internet traffic.
Security Groups and Network ACLs – Both must allow the traffic for the connection to succeed.
No Additional Cost for the Gateway Itself – Generally, cloud providers do not charge for creating an Internet Gateway, but they do charge for data transfer.

Typical Use in Cloud Networking

In an IT environment, the Internet Gateway is typically used to:

Allow cloud servers to download patches, updates, and software from the internet.
Enable public-facing applications (such as websites or APIs) to be accessed over the internet.
Provide remote access to administrators through secure connections (like SSH or RDP).