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Amazon Web Services AWS Broken Labs

Lab 06 - VPC NAT Gateway

Difficulty: Advanced Service: Amazon VPC

Cost: This lab uses a t2.micro instance plus three VPC interface endpoints. Estimated cost if left running: approximately $1.00/day. Delete the stack when you are done.

Note: Any services created outside of CloudFormation must be deleted manually before deleting the stack.

Scenario

Your team deployed an EC2 instance in a private subnet for security. The instance is running and you can connect to it using Session Manager. But the operations team reports that the instance cannot reach the internet — outbound connections are timing out and package installations are failing.

The VPC has an Internet Gateway and a correctly configured public subnet. Your job is to diagnose why the private instance has no outbound internet connectivity and fix it.

What Was Deployed

Resource Purpose
AWS::EC2::VPC Custom VPC for the lab (10.0.0.0/16)
AWS::EC2::Subnet (x2) Public subnet (10.0.1.0/24) and private subnet (10.0.2.0/24)
AWS::EC2::InternetGateway Internet Gateway — created and attached to the VPC
AWS::EC2::RouteTable (x2) Public route table (has 0.0.0.0/0 → IGW) and private route table
AWS::EC2::VPCEndpoint (x3) Interface endpoints for SSM, SSMMessages, EC2Messages
AWS::IAM::Role IAM role with AmazonSSMManagedInstanceCore for Session Manager access
AWS::EC2::Instance t2.micro in the private subnet — no public IP

The stack deployed without errors. The instance is running. Session Manager connectivity works via the VPC endpoints.

Deploy the Lab

  1. Open the AWS CloudFormation console
  2. Click Create stack > With new resources (standard)
  3. Select Upload a template file and upload lab-06-private-subnet.yaml

  4. Enter a stack name (e.g., brokenlabs-vpc-lab-06) and click Next > Next > Submit

    IAM notice: This template creates an IAM role. On the final confirmation page, check the box acknowledging that CloudFormation will create IAM resources, then click Submit.

  5. Wait for the stack status to reach CREATE_COMPLETE (takes 3–5 minutes)
  6. Open the stack Outputs tab — you will see InstanceId and PrivateIP

The Problem

Connect to the instance using Session Manager:

  1. Open the EC2 console > Instances
  2. Select the instance named brokenlabs-vpc-lab-06
  3. Click Connect > Session Manager tab > Connect

Once connected, test outbound internet access:

curl --max-time 5 https://checkip.amazonaws.com

Expected: The public IP address of the instance is returned. Actual: The connection times out — the instance cannot reach the internet.

The instance is healthy and Session Manager works. Only outbound internet access is failing.

Fix the Lab

The private subnet has a route table but no route to the internet. The public subnet already has internet access via the Internet Gateway. Think about what component sits between a private subnet and the internet, and what route the private subnet needs to reach it.

After applying the fix, reconnect via Session Manager and re-run the curl command to confirm the instance can now reach the internet.

Need help? Open hints.md for progressive hints.

Resources