What are AWS VPC and Networking?

Question

Accepted Answer

**VPC (Virtual Private Cloud)** — virtual network in AWS.

**Key components:** Subnet, Internet Gateway, NAT Gateway, Security Groups, NACLs.

**Typical architecture:**
```text
VPC (10.0.0.0/16)
  ├── Public Subnet AZ-1 (10.0.1.0/24)  → ALB, Bastion
  ├── Public Subnet AZ-2 (10.0.2.0/24)  → ALB, Bastion
  ├── Private Subnet AZ-1 (10.0.3.0/24) → ECS/EKS
  ├── Private Subnet AZ-2 (10.0.4.0/24) → ECS/EKS
  ├── Private Subnet AZ-1 (10.0.5.0/24) → RDS (primary)
  └── Private Subnet AZ-2 (10.0.6.0/24) → RDS (standby)
```

**Security Group (Terraform):**
```hcl
resource "aws_security_group" "web" {
  name   = "web-sg"
  vpc_id = aws_vpc.main.id

ingress {
    from_port   = 443
    to_port     = 443
    protocol    = "tcp"
    cidr_blocks = ["0.0.0.0/0"]
  }

egress {
    from_port   = 0
    to_port     = 0
    protocol    = "-1"
    cidr_blocks = ["0.0.0.0/0"]
  }
}
```

**Best practices:** Multi-AZ, private subnets for databases, VPC Endpoints, Flow Logs.

DevOps: What are AWS VPC and Networking?