Building a Multi-VPC Architecture on AWS

Source: Dev.to

Introduction

When people begin learning cloud networking, they often start with a single VPC.
Organizations separate workloads for:

• Security
• Scalability
• Team isolation
• Environment segmentation (Dev, Staging, Production)

A common question then arises: How do these isolated networks communicate with each other securely?
This hands‑on project explores that question.

In this guide you will:

• Create two separate VPCs
• Design public and private subnets in each VPC
• Establish a VPC Peering connection
• Configure route tables to enable communication

By the end, you’ll have a basic multi‑VPC architecture similar to what is used in real production environments.

Core Networking Concepts Covered

• Network isolation
• CIDR block design
• Routing between networks
• Private communication without the internet

These skills are foundational for Cloud Engineers, DevOps Engineers, and Solutions Architects.

Architecture Overview

VPC-A (10.10.0.0/16)          VPC-B (10.20.0.0/16)
----------------------        ----------------------
Public Subnet                Public Subnet
Private Subnet               Private Subnet
        |                          |
        -------- VPC Peering -------

No Internet Gateway or NAT Gateway is required; this is purely internal communication.

Step‑by‑Step Implementation

1. Create VPC‑A

• Name: VPC‑A
• CIDR block: 10.10.0.0/16

2. Create Subnets in VPC‑A

3. Create VPC‑B

• Name: VPC‑B
• CIDR block: 10.20.0.0/16

4. Create Subnets in VPC‑B

5. Create a VPC Peering Connection

1. Open VPC Dashboard → Peering Connections.
2. Click Create Peering Connection.
3. Select VPC‑A as the requester and VPC‑B as the accepter.
4. Create and then accept the request.

6. Configure Route Tables

VPC‑A Route Table

VPC‑B Route Table

Without these routes, traffic will not flow even though the peering connection exists.

7. Validate Connectivity

1. Launch EC2 instances in each VPC (use the private subnets).
2. From one instance, ping the private IP of the other instance.

If configured correctly, the instances should communicate successfully.

Important Considerations

• No transitive routing: A → B → C will not work automatically; each peering relationship must be explicitly defined.
• CIDR blocks must not overlap.
• Each route must be manually configured for the desired traffic flow.

What This Project Teaches You

• How real‑world architectures are segmented.
• Differences between cloud networking and traditional networking.
• How routing enables communication across isolated networks.
• Designing secure, isolated systems.

Real‑World Use Cases

• Connecting Development and Production environments.
• Separating application tiers (e.g., web tier vs. database tier).
• Multi‑team architectures where each team owns its own VPC.
• Microservices communication across VPCs.