Virtual Private Cloud (VPC)

• A logically isolated virtual network within a public cloud provider’s infrastructure that gives you complete control over your network environment
• Acts as your own private section of the cloud where you can launch resources in a virtual network that you define
• Combines the scalability and convenience of public cloud computing with the isolation and control of private networking
• Essential bridge between traditional on-premises networking concepts and cloud infrastructure

Core VPC Components

• Subnets: Subdivisions of your VPC’s IP address range where you actually place resources
  • Public subnets: Have routes to an Internet Gateway (resources get public IPs)
  • Private subnets: No direct internet access (resources use NAT for outbound only)
• Route Tables: Control where network traffic is directed from subnets
• Internet Gateway (IGW): Provides internet access to public subnets
• NAT Gateway/Instance: Allows private subnet resources to access internet without being directly accessible
• Security Groups: Virtual firewalls that control inbound/outbound traffic at the instance level
• Network ACLs: Additional firewall layer that operates at the subnet level

VPC Addressing and Routing

• Uses RFC 1918 private IP address ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16)
• Cannot change VPC CIDR block after creation (in most cloud providers)
• Subnet CIDR blocks must be subsets of VPC CIDR and cannot overlap
• Each subnet exists in a single Availability Zone but VPC can span multiple AZs
• Default route (0.0.0.0/0) points to IGW for internet access in public subnets