AWS VPC Basics: Subnets & Gateways Explained

Today I stepped into the networking side of AWS — learning about the backbone of secure and scalable cloud deployments: Amazon VPC (Virtual Private Cloud).

Mastering networking in the cloud is essential for building production-ready, secure, and scalable architectures. Whether it's hosting a secure app, launching a database, or creating a multi-tier application — it all starts with VPC!

🔍 What is a VPC?

A Virtual Private Cloud (VPC) is a logically isolated network inside AWS that you define. You can control:

IP address ranges (CIDR blocks)
Subnets
Route tables
Internet access
Firewalls
Gateways

It’s like having your own virtual data center — where you can run resources (like EC2, RDS, Lambda) in a highly secure and customizable environment.

🧩 Core VPC Components I Explored Today:

🔸 1. Subnets

A subnet is a segment of a VPC's IP address range where you can place AWS resources. There are two types:

Public Subnet – Connected to the internet via Internet Gateway.
Private Subnet – No direct access to the internet (great for databases, backend services).

You can split your application architecture:

Frontend in a public subnet
Backend or DB in a private subnet

🔸 2. Internet Gateway (IGW)

An Internet Gateway enables instances in a public subnet to connect to the internet. Without it, your EC2 instances in public subnets cannot access or be accessed from the web.

✅ I attached an IGW to my VPC
✅ Updated route tables to allow 0.0.0.0/0 access through IGW

🔸 3. NAT Gateway

A NAT (Network Address Translation) Gateway allows instances in private subnets to access the internet (for updates, packages) without being exposed to inbound internet traffic.

✅ I placed the NAT Gateway in a public subnet
✅ Added a route in private subnet’s route table to point 0.0.0.0/0 to the NAT Gateway
✅ Tested internet access from EC2 in private subnet → Worked perfectly!

💡 Why Use Public & Private Subnets?

Separating your application tiers into public and private subnets boosts security. For example:

Web server (NGINX): Public subnet
Database (MySQL/PostgreSQL): Private subnet
Backend service: Private subnet
NAT Gateway: Public subnet

This setup is the backbone of multi-tier architecture, where each layer is isolated and follows the principle of least privilege.

🛠 Hands-on Tasks I Completed:

1️⃣ Created a custom VPC with custom CIDR block
2️⃣ Added 2 public and 2 private subnets across multiple availability zones
3️⃣ Attached and configured an Internet Gateway
4️⃣ Created a NAT Gateway in a public subnet
5️⃣ Set up custom route tables
6️⃣ Launched EC2 instances in both subnet types
7️⃣ Connected via SSH and tested access/connectivity
8️⃣ Verified internet access from private subnet via NAT

🧠 Key Learnings:

✅ How routing works between private/public subnets
✅ Why NAT Gateway is essential for secure outbound traffic
✅ How Internet Gateway enables global access to cloud servers
✅ How to isolate workloads and restrict public access
✅ Difference between Security Groups and Route Tables

🌍 Real-World Use Cases of VPC:

🔹 Host static or dynamic web apps with secure backends
🔹 Run databases securely without internet exposure
🔹 Set up secure hybrid networks with VPN or Direct Connect
🔹 Create multi-tier application environments (frontend, backend, DB)
🔹 Build isolated test environments or dev/staging infrastructure

🔐 Best Practices I Noted:

🔐 Keep all critical services (e.g., DB, APIs) in private subnets
🔐 Enable VPC Flow Logs for monitoring and troubleshooting
🔐 Use IAM roles, not hardcoded credentials
🔐 Use Security Groups for instance-level security and NACLs for subnet-level
🔐 Avoid assigning public IPs unnecessarily
🔐 Use multiple AZs for high availability

📌 What’s Next?

🔄 Tomorrow (Day 12):
I’ll dive deeper into:

Route Tables
Security Groups vs NACLs
VPC Peering — how to connect multiple VPCs together

📸 Want Visuals?

🖼️ I’m also creating a visual diagram of my VPC layout and subnet routing — stay tuned on my LinkedIn!

🔗 And here's a static portfolio site I hosted earlier on S3 + CloudFront from Day 9:
👉 View Project on LinkedIn

🚀 Final Thoughts:

AWS VPC is the network foundation for everything you build in the cloud. It connects, isolates, secures, and scales your infrastructure. Without a strong grasp on VPC fundamentals, real-world cloud deployments can become a tangled mess.

This hands-on practice was crucial in understanding how everything works under the hood in cloud networking.

🏷️ Hashtags:

#Day11 #30DaysOfCloud #AWS #VPC #Subnets #NATGateway #IGW #CloudNetworking #DevOps #LearnInPublic #Hashnode #TruptiMane #CloudSecurity #AWSBeginner #AmazonWebServices #CloudJourney

✅ Day 11 of My Cloud Journey ☁ – AWS VPC Basics: Subnets, IGW & NAT Gateway Explained 🛡️🌐

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