Securing your VPC using Public and Private Subnets (NAT Instance)

In this lab, you will design a VPC with a public subnet, a private subnet, and a Network Address Translation (NAT) device in the public subnet. For NAT devices, it is generally recommended to utilize a NAT Gateway over creating your own NAT instance. However, this lab will go through the process of creating a NAT instance in case you'd like to be able to customize the EC2 instance used for network address translation. The NAT Gateway version of this lab replaces the NAT instance lab step with one that walks you through configuring a NAT Gateway.

A NAT device enables instances in the private subnet to initiate outbound traffic to the Internet. This scenario is common when you have a public-facing web application while maintaining back-end servers that aren't publicly accessible.

A common example is a multi-tier website, with the web servers in a public subnet, and the database servers in a private subnet. You can set up security and routing allowing the web servers to communicate with the database servers. The instances in the public subnet can send outbound traffic directly to the Internet, whereas the instances in the private subnet cannot. The instances in the private subnet can access the Internet via the NAT instance in the public subnet. In this Lab, you will also increase the network security using a network access control list (NACL), which is an optional layer of security that acts as a firewall for controlling traffic in and out of a subnet. After completing this lab, you might consider setting up network ACLs with rules similar to your security groups, in order to add an additional layer of security to your VPC.

 

Learning Objectives

Upon completion of this lab you will be able to create, configure and test the following:

• Virtual Private Cloud (VPC)
• Internet Gateway
• Public and private subnets (inbound/outbound rules)
• Security groups (inbound/outbound rules for multiple purposes)
• Network access control lists (NACLs) for additional security on a private subnet
• Bastion host for SSH access from the internet to private instances
• Network Address Translation (NAT) Instance to grant access for private instances to perform operating system updates
• Route tables associated with public and private subnets

Intended Audience

• Candidates for the AWS Cloud Practitioner Exam
• Candidates for the AWS Solutions Architect Associate Exam

Prerequisites

You should be familiar with:

• Elastic Cloud Compute (EC2) basics
• Conceptual understanding of Virtual Private Clouds (VPCs), subnets, network route tables, firewalls, private and public IP addresses
• Some Linux shell/command level understanding is helpful, but not required

Lab Environment

After completing the lab instructions, the environment should look similar to:

Updates

October 26th, 2022 -  Updated screenshots and instructions for changes in the UI & Linux AMIs

December 29th, 2021 - Provided additional information regarding the time out encountered in the Lab

June 29th, 2021 - Updated lab step format and screenshots

June 8th, 2020 - Added troubleshooting instructions to ensure SSH agent forwarding is enabled when connecting to the bastion host from Windows

August 16th, 2019 - Increased the maximum allowed time on the Lab to allow for a better-paced learning environment

January 10th, 2019 - Added a validation Lab Step to check the work you perform in the Lab

September 7th, 2018 - Updated instructions and screenshots to the latest VPC and EC2 user interfaces

May 24th, 2018 - Clarified instructions for connecting to the EC2 instances on Windows.