VPC and EC2 Implementation

Key Takeaways

VPC as Network Isolation: A Virtual Private Cloud (VPC) creates a completely isolated network within an AWS region that separates your resources from everyone else's. While millions deploy to the same region, each VPC ensures your infrastructure remains private and protected within its own network boundary.

Regions vs Availability Zones: AWS regions contain multiple physical data centers called availability zones. Your VPC spans the entire region, but subnets exist within a single availability zone. Deploy resources across multiple AZs for high availability - if one data center fails, your services in other AZs stay online.

Public vs Private Subnets: Public subnets have routes to an internet gateway, giving resources public IP addresses accessible from the internet. Private subnets lack this route, isolating resources like databases from direct internet access. Production systems typically use one public-private subnet pair per AZ, placing load balancers in public subnets and application servers in private ones.

CIDR Block IP Addressing: The notation 10.0.0.0/16 uses CIDR to define IP ranges. The /16 prefix means the first 16 bits (10.0) are fixed, while the remaining bits can vary from 0-255, creating 65,536 possible IP addresses for resources in your VPC.

SSH Key Pair Authentication: EC2 instances use public-private key pairs for secure access. AWS stores the public key on your instance, you keep the private key locally. When connecting via SSH, your client generates a signature from the private key that AWS verifies against the public key, granting access only if they match.

EBS Volume Storage Separation: EC2 instances have a root volume containing the operating system. Never mix application data with OS files - attach separate EBS volumes for application data persistence. This ensures your data survives even if the EC2 instance terminates.