Fixing AWS VPC Connectivity

When I took on the Networking Quest in AWS , I ran into a classic issue that many cloud engineers face — EC2 instances with no internet access and broken app connectivity.

Here’s a breakdown of what I did and what I learned along the way.

The Problem

After deploying web and database servers to AWS, the following issues were noticed:

  • The EC2 instances couldn’t reach the internet.
  • The web server couldn’t talk to the database.

Turns out — VPC misconfiguration was the root cause.

Architecture Diagram

Arch

The Fix – Step by Step

1. Set up Public and Private Subnets

  • 10.10.0.0/24 for the public subnet (web server)
  • 10.10.2.0/24 for the private subnet (DB server)

2. Attach an Internet Gateway

  • Created and attached an IGW to the VPC
  • Updated the public subnet’s route table to allow 0.0.0.0/0 via IGW

3. Assign Public IP to Web Server

  • Made the web server reachable via HTTP from the internet

4. Security Groups

  • Web server: Open port 80 for all (0.0.0.0/0)
  • DB server: Open port 3306 only to the web server’s private IP

5. Why the DB Server Couldn’t Connect?

  • It was in a private subnet with no NAT or IGW — by design!
  • Only internal connections from the web server were allowed

Takeaways

  • Always verify route tables and subnet associations.
  • Assign a public IP only when necessary.
  • Use security groups for precise, layered control.

Bonus Tip

Create a reusable Terraform module to automate this setup — makes you look sharp in interviews!

Thanks for reading!
Feel free to check out the GitHub repo here.