VPC — Overview

What it is, why it matters, architecture and key concepts

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Written by senior engineers. Reviewed for technical accuracy.· Updated 2025 · SynfraCore VPC Team

Expert Content

AWS VPC — Your Private Network in the Cloud

A VPC (Virtual Private Cloud) is your own isolated network inside AWS. When you launch EC2 instances, RDS databases, or Lambda functions — they all live inside a VPC. You control the IP ranges, subnets, routing, and firewalls.

VPC Architecture

Public vs Private Subnets

	Public Subnet	Private Subnet

|---|---|---|

Internet access	Direct via IGW	Outbound only via NAT
What lives here	Load balancers, NAT Gateway	App servers, databases
Public IP	Assigned automatically	No public IP
Security	Exposed to internet	Protected

💡 Design Rule

Load Balancers → Public subnet (need internet access)

App Servers → Private subnet (only ALB needs to reach them)

Databases → Private subnet with NO internet route

Security Groups vs Network ACLs

Quick Setup with AWS CLI

bash

# Create VPC
aws ec2 create-vpc --cidr-block 10.0.0.0/16 \
    --tag-specifications 'ResourceType=vpc,Tags=[{Key=Name,Value=prod-vpc}]'

# Create public subnet
aws ec2 create-subnet --vpc-id vpc-xxx \
    --cidr-block 10.0.1.0/24 --availability-zone us-east-1a

# Create Internet Gateway and attach
aws ec2 create-internet-gateway
aws ec2 attach-internet-gateway --vpc-id vpc-xxx --internet-gateway-id igw-xxx

# Add route for public subnet
aws ec2 create-route --route-table-id rtb-xxx \
    --destination-cidr-block 0.0.0.0/0 --gateway-id igw-xxx

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