Building Secure Networks with Amazon VPC: A Complete Architecture Walkthrough

Introduction to Amazon VPC

Amazon Virtual Private Cloud (VPC) is a logically isolated section of the AWS cloud where you can launch AWS resources in a virtual network that you define. It gives you full control over your network setup, including:

• IP address ranges
  
  

• Subnets
  
  

• Route tables
  
  

• Network gateways
  
  

• Security settings
  
  

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 Key Building Blocks of a Secure VPC Architecture

1. CIDR Block Planning

• Choose an appropriate CIDR range (e.g., 10.0.0.0/16) to avoid overlap with on-prem or other VPCs.
  
  

• Plan for subnet segmentation by reserving smaller CIDR blocks.
  
  

2. Subnets

• Public Subnets: For internet-facing services like ALB, NAT Gateway.
  
  

• Private Subnets: For databases, internal services.
  
  

• Isolated Subnets: No route to the internet—used for critical data.
  
  

3. Internet Gateway (IGW)

• Needed for outbound traffic from public subnets to the internet.
  
  

4. NAT Gateway

• Allows outbound internet access for private subnets while blocking inbound connections.
  
  

• Deploy in a highly available setup across multiple AZs.
  
  

5. Route Tables

• Define traffic direction.
  
  

• Associate public subnets with a route to IGW.
  
  

• Associate private subnets with a route to NAT Gateway.
  
  

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 Enhancing Security: Network Controls and Identity

1. Security Groups

• Stateful firewalls attached to resources.
  
  

• Allow only necessary inbound/outbound traffic (e.g., HTTP, HTTPS, SSH).
  
  

2. Network Access Control Lists (NACLs)

• Stateless filtering at the subnet level.
  
  

• Add a layer of defense by controlling ingress/egress at the subnet boundary.
  
  

3. VPC Flow Logs

• Capture information about IP traffic going to and from network interfaces.
  
  

• Send to Amazon CloudWatch or S3 for monitoring and analysis.
  
  

4. PrivateLink & VPC Endpoints

• Securely connect to AWS services without traversing the internet.
  
  

• Supports service-to-service communication within AWS securely.
  
  

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 Sample Architecture Design

Scenario: Multi-Tier Web Application

• Public Subnet: Hosts Application Load Balancer (ALB).
  
  

• Private Subnet: Hosts EC2 instances (App tier) and RDS (DB tier).
  
  

• NAT Gateway: Deployed in public subnet for EC2 outbound access.
  
  

• ALB: Routes traffic to EC2 based on path-based routing rules.
  
  

• RDS Subnet Group: Located in private subnets with no direct internet access.
  
  

High Availability Strategy:

• Distribute subnets across at least two AZs.
  
  

• Deploy NAT Gateways in each AZ for redundancy.
  
  

• Use Auto Scaling Groups with health checks behind the ALB.
  
  

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 Monitoring and Logging

• Enable CloudTrail: Track all API activity.
  
  

• Use AWS Config: Monitor resource configurations for compliance.
  
  

• Set up CloudWatch Alarms: Trigger alerts on metrics like CPU, memory, and VPC anomalies.
  
  

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 Testing and Validation

• Perform port scans and penetration tests (with AWS permission).
  
  

• Validate that:
  
  

• No unintended open ports exist.
  
  

• Private instances cannot be reached directly from the internet.
  
  

• Logging is capturing all relevant activity.
  
  

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 Best Practices Summary

• Use least privilege principle in Security Groups.
  
  

• Disable public IP assignment for private subnet instances.
  
  

• Deploy multi-AZ resources for fault tolerance.
  
  

• Encrypt traffic and data at rest using KMS.

• Regularly review access logs and VPC Flow Logs.