aws-vpc

What this skill does

# AWS VPC

Design and manage Virtual Private Cloud networking for production AWS environments with proper subnet isolation, routing, and security.

## When to Use This Skill

- Building a new VPC for production, staging, or development
- Setting up public/private subnet architecture across multiple AZs
- Configuring NAT Gateways for private subnet internet access
- Creating security groups and NACLs for network segmentation
- Setting up VPC peering or Transit Gateway for multi-VPC connectivity
- Implementing VPC endpoints for private access to AWS services
- Troubleshooting connectivity issues between resources

## Prerequisites

- AWS CLI v2 installed and configured
- IAM permissions: `ec2:*` (or scoped to VPC-related actions)
- CIDR range planning completed (avoid overlaps with on-premises or other VPCs)
- For VPC peering: access to both VPCs (same or different accounts)

## Network Architecture

```
VPC (10.0.0.0/16) - 65,536 IPs
├── Public Subnets (internet-facing via IGW)
│   ├── 10.0.1.0/24 (us-east-1a) - 256 IPs - ALBs, NAT GW, bastion
│   ├── 10.0.2.0/24 (us-east-1b) - 256 IPs
│   └── 10.0.3.0/24 (us-east-1c) - 256 IPs
├── Private Subnets (app tier, NAT GW for outbound)
│   ├── 10.0.11.0/24 (us-east-1a) - 256 IPs - ECS, EC2, Lambda
│   ├── 10.0.12.0/24 (us-east-1b) - 256 IPs
│   └── 10.0.13.0/24 (us-east-1c) - 256 IPs
├── Data Subnets (isolated, no internet)
│   ├── 10.0.21.0/24 (us-east-1a) - 256 IPs - RDS, ElastiCache
│   ├── 10.0.22.0/24 (us-east-1b) - 256 IPs
│   └── 10.0.23.0/24 (us-east-1c) - 256 IPs
├── Internet Gateway
├── NAT Gateways (one per AZ for HA)
├── Route Tables (public, private, data)
└── VPC Flow Logs → CloudWatch / S3
```

## Create a VPC with CLI

```bash
# Create the VPC
VPC_ID=$(aws ec2 create-vpc \
  --cidr-block 10.0.0.0/16 \
  --tag-specifications 'ResourceType=vpc,Tags=[{Key=Name,Value=production-vpc},{Key=Environment,Value=production}]' \
  --query 'Vpc.VpcId' --output text)

# Enable DNS support and hostnames
aws ec2 modify-vpc-attribute --vpc-id $VPC_ID --enable-dns-support '{"Value":true}'
aws ec2 modify-vpc-attribute --vpc-id $VPC_ID --enable-dns-hostnames '{"Value":true}'

# Create public subnets
PUB_SUB_A=$(aws ec2 create-subnet \
  --vpc-id $VPC_ID \
  --cidr-block 10.0.1.0/24 \
  --availability-zone us-east-1a \
  --tag-specifications 'ResourceType=subnet,Tags=[{Key=Name,Value=public-a},{Key=Tier,Value=public}]' \
  --query 'Subnet.SubnetId' --output text)

PUB_SUB_B=$(aws ec2 create-subnet \
  --vpc-id $VPC_ID \
  --cidr-block 10.0.2.0/24 \
  --availability-zone us-east-1b \
  --tag-specifications 'ResourceType=subnet,Tags=[{Key=Name,Value=public-b},{Key=Tier,Value=public}]' \
  --query 'Subnet.SubnetId' --output text)

# Enable auto-assign public IP on public subnets
aws ec2 modify-subnet-attribute --subnet-id $PUB_SUB_A --map-public-ip-on-launch
aws ec2 modify-subnet-attribute --subnet-id $PUB_SUB_B --map-public-ip-on-launch

# Create private subnets
PRIV_SUB_A=$(aws ec2 create-subnet \
  --vpc-id $VPC_ID \
  --cidr-block 10.0.11.0/24 \
  --availability-zone us-east-1a \
  --tag-specifications 'ResourceType=subnet,Tags=[{Key=Name,Value=private-a},{Key=Tier,Value=private}]' \
  --query 'Subnet.SubnetId' --output text)

PRIV_SUB_B=$(aws ec2 create-subnet \
  --vpc-id $VPC_ID \
  --cidr-block 10.0.12.0/24 \
  --availability-zone us-east-1b \
  --tag-specifications 'ResourceType=subnet,Tags=[{Key=Name,Value=private-b},{Key=Tier,Value=private}]' \
  --query 'Subnet.SubnetId' --output text)

# Create data subnets (isolated)
DATA_SUB_A=$(aws ec2 create-subnet \
  --vpc-id $VPC_ID \
  --cidr-block 10.0.21.0/24 \
  --availability-zone us-east-1a \
  --tag-specifications 'ResourceType=subnet,Tags=[{Key=Name,Value=data-a},{Key=Tier,Value=data}]' \
  --query 'Subnet.SubnetId' --output text)

DATA_SUB_B=$(aws ec2 create-subnet \
  --vpc-id $VPC_ID \
  --cidr-block 10.0.22.0/24 \
  --availability-zone us-east-1b \
  --tag-specifications 'ResourceType=subnet,Tags=[{Key=Name,Value=data-b},{Key=Tier,Value=data}]' \
  --query 'Subnet.SubnetId' --output text)
```

## Internet Gateway and NAT Gateway

```bash
# Create and attach Internet Gateway
IGW_ID=$(aws ec2 create-internet-gateway \
  --tag-specifications 'ResourceType=internet-gateway,Tags=[{Key=Name,Value=production-igw}]' \
  --query 'InternetGateway.InternetGatewayId' --output text)
aws ec2 attach-internet-gateway --vpc-id $VPC_ID --internet-gateway-id $IGW_ID

# Create public route table
PUB_RT=$(aws ec2 create-route-table \
  --vpc-id $VPC_ID \
  --tag-specifications 'ResourceType=route-table,Tags=[{Key=Name,Value=public-rt}]' \
  --query 'RouteTable.RouteTableId' --output text)
aws ec2 create-route --route-table-id $PUB_RT --destination-cidr-block 0.0.0.0/0 --gateway-id $IGW_ID
aws ec2 associate-route-table --route-table-id $PUB_RT --subnet-id $PUB_SUB_A
aws ec2 associate-route-table --route-table-id $PUB_RT --subnet-id $PUB_SUB_B

# Allocate Elastic IPs for NAT Gateways (one per AZ for HA)
EIP_A=$(aws ec2 allocate-address --domain vpc --query 'AllocationId' --output text)
EIP_B=$(aws ec2 allocate-address --domain vpc --query 'AllocationId' --output text)

# Create NAT Gateways in public subnets
NAT_A=$(aws ec2 create-nat-gateway \
  --subnet-id $PUB_SUB_A \
  --allocation-id $EIP_A \
  --tag-specifications 'ResourceType=natgateway,Tags=[{Key=Name,Value=nat-a}]' \
  --query 'NatGateway.NatGatewayId' --output text)

NAT_B=$(aws ec2 create-nat-gateway \
  --subnet-id $PUB_SUB_B \
  --allocation-id $EIP_B \
  --tag-specifications 'ResourceType=natgateway,Tags=[{Key=Name,Value=nat-b}]' \
  --query 'NatGateway.NatGatewayId' --output text)

# Wait for NAT Gateways
aws ec2 wait nat-gateway-available --nat-gateway-ids $NAT_A $NAT_B

# Create private route tables (one per AZ for HA NAT)
PRIV_RT_A=$(aws ec2 create-route-table \
  --vpc-id $VPC_ID \
  --tag-specifications 'ResourceType=route-table,Tags=[{Key=Name,Value=private-rt-a}]' \
  --query 'RouteTable.RouteTableId' --output text)
aws ec2 create-route --route-table-id $PRIV_RT_A --destination-cidr-block 0.0.0.0/0 --nat-gateway-id $NAT_A
aws ec2 associate-route-table --route-table-id $PRIV_RT_A --subnet-id $PRIV_SUB_A

PRIV_RT_B=$(aws ec2 create-route-table \
  --vpc-id $VPC_ID \
  --tag-specifications 'ResourceType=route-table,Tags=[{Key=Name,Value=private-rt-b}]' \
  --query 'RouteTable.RouteTableId' --output text)
aws ec2 create-route --route-table-id $PRIV_RT_B --destination-cidr-block 0.0.0.0/0 --nat-gateway-id $NAT_B
aws ec2 associate-route-table --route-table-id $PRIV_RT_B --subnet-id $PRIV_SUB_B
```

## Security Groups

```bash
# ALB security group (public-facing)
ALB_SG=$(aws ec2 create-security-group \
  --group-name alb-sg \
  --description "Application Load Balancer" \
  --vpc-id $VPC_ID \
  --query 'GroupId' --output text)
aws ec2 authorize-security-group-ingress --group-id $ALB_SG --protocol tcp --port 443 --cidr 0.0.0.0/0
aws ec2 authorize-security-group-ingress --group-id $ALB_SG --protocol tcp --port 80 --cidr 0.0.0.0/0

# Application security group (only from ALB)
APP_SG=$(aws ec2 create-security-group \
  --group-name app-sg \
  --description "Application tier" \
  --vpc-id $VPC_ID \
  --query 'GroupId' --output text)
aws ec2 authorize-security-group-ingress \
  --group-id $APP_SG \
  --protocol tcp \
  --port 8080 \
  --source-group $ALB_SG

# Database security group (only from app tier)
DB_SG=$(aws ec2 create-security-group \
  --group-name db-sg \
  --description "Database tier" \
  --vpc-id $VPC_ID \
  --query 'GroupId' --output text)
aws ec2 authorize-security-group-ingress \
  --group-id $DB_SG \
  --protocol tcp \
  --port 5432 \
  --source-group $APP_SG

# List all security groups in the VPC
aws ec2 describe-security-groups \
  --filters "Name=vpc-id,Values=$VPC_ID" \
  --query "SecurityGroups[].{Name:GroupName,ID:GroupId,Description:Description}" \
  --output table
```

## VPC Endpoints (Private Access to AWS Services)

```bash
# Gateway endpoint for S3 (free, route-table based)
aws ec2