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Amazon Web Services AWS Broken Labs

Hints — VPC Settings - Lab 05

Open each hint only after you’ve spent time investigating on your own.

Hint 1 — Look at the Outputs

Open the Outputs tab for your CloudFormation stack. Look at the WebPageURL value.

A normal URL looks like:

http://ec2-1-2-3-4.compute-1.amazonaws.com/

What does your WebPageURL show instead? What part of the URL is missing?

Hint 2 — The instance itself

The InstancePublicIP Output contains the instance’s public IP address.

Try opening that address directly in your browser: http://<InstancePublicIP>/

Does the page load? If yes, the web server is running correctly. The issue is not with the instance or the web server — something is preventing the instance from being assigned the type of address that should appear in WebPageURL.

Hint 3 — VPC-level settings

EC2 instances receive different types of addresses depending on how the VPC is configured. A public IP address is assigned when the subnet has auto-assign enabled. Another type of address — the one missing from the URL — is controlled separately at the VPC level.

Navigate to the VPC console > Your VPCs. Select brokenlabs-vpc-lab-05-vpc and look at the Details tab.

Find the settings that relate to how instances in this VPC are addressed. Is everything enabled?

Spoiler Alert — Full Solution

Root cause: The VPC has DNS hostnames disabled. When this setting is off, EC2 instances in the VPC are not assigned public DNS hostnames — only a public IP address. The WebPageURL Output used the DNS hostname, which was empty at stack creation time, producing the broken http:/// URL.

To fix:

  1. Open the VPC console and go to Your VPCs
  2. Select the VPC named brokenlabs-vpc-lab-05-vpc
  3. Click Actions > Edit VPC settings
  4. Check the box for Enable DNS hostnames
  5. Click Save
  6. Navigate to the EC2 console > Instances
  7. Select brokenlabs-vpc-lab-05 and find the Public IPv4 DNS field
  8. Open http://<public-ipv4-dns>/ in your browser — the AWS Broken Labs page should appear

Note: The WebPageURL in CloudFormation Outputs was captured at stack creation and will still show http:///. Use the DNS name from the EC2 console directly.