AWS VPC Networking

Isolated cloud network with subnets, route tables, NAT, VPC peering, and Transit Gateway.

AWSAdvanced

Why

VPC isolates resources in your own network — private subnets, controlled egress via NAT, and peering between accounts. Required for RDS/ECS/EKS.

Default VPC is too open for production.

When

Create custom VPC for any production workload — multi-AZ subnets, private + public, NAT for egress. Avoid default VPC (public subnets, open SG).

How

1. Create VPC — aws ec2 create-vpc --cidr-block 10.0.0.0/16 2. Subnets — 2+ per AZ, public (IGW route) + private (NAT route) 3. Internet Gateway — attach to VPC, route 0.0.0.0/0 in public RT 4. NAT Gateway — in public subnet, private RT routes 0.0.0.0/0 to NAT 5. Security groups — stateful, allow by SG reference (app SG → DB SG 5432) 6. NACLs — stateless subnet-level, default allow all (use SGs primarily) 7. VPC peering — connect VPCs, same/different accounts, non-overlapping CIDR 8. Transit Gateway — hub for many VPCs, scales better than peering mesh

Example

# Terraform — production VPC with private subnets + NAT resource "aws_vpc" "main" { cidr_block = "10.0.0.0/16" enable_dns_hostnames = true } resource "aws_subnet" "private" { count = 3 vpc_id = aws_vpc.main.id cidr_block = "10.0.${count.index + 1}.0/24" availability_zone = data.aws_availability_zones.available.names[count.index] } resource "aws_nat_gateway" "nat" { allocation_id = aws_eip.nat.id subnet_id = aws_subnet.public[0].id } # Route private subnet egress through NAT resource "aws_route" "private_egress" { route_table_id = aws_route_table.private.id destination_cidr_block = "0.0.0.0/0" nat_gateway_id = aws_nat_gateway.nat.id }

Common Problems

⚠NAT Gateway cost — $0.045/GB egress, high traffic costs more than the app
⚠CIDR overlap blocks peering — plan CIDR ranges upfront, use /16 per VPC
⚠Default VPC too open — public subnets + open SG, never use for production

Best Practices

✓Use VPC Reachability Analyzer — verifies connectivity before deploying
✓One NAT per AZ — HA, avoids single NAT becoming cross-AZ bottleneck
✓Use Transit Gateway for 3+ VPCs — simpler than peering mesh, central routing

FAQ

What is AWS VPC Networking and what problem does it solve?

Isolated cloud network with subnets, route tables, NAT, VPC peering, and Transit Gateway. It lets developers deploy, store, and scale without self-managing infrastructure — a core reference for cloud service selection.

How do I get started with AWS VPC Networking in 5 minutes?

Two steps to run it: (1) Create VPC — aws ec2 create-vpc --cidr-block 10.0.0.0/16; (2) Subnets — 2+ per AZ, public (IGW route) + private (NAT route). Validate on the free tier first, then wire into production.

What is the #1 pitfall with AWS VPC Networking?

The most frequent issue is: NAT Gateway cost — $0.045/GB egress, high traffic costs more than the app. Run a pre-launch checklist item by item, and add policy/config scanning in CI.

What are the best practices for AWS VPC Networking?

Best practices for AWS VPC Networking include: Use VPC Reachability Analyzer — verifies connectivity before deploying; One NAT per AZ — HA, avoids single NAT becoming cross-AZ bottleneck; Use Transit Gateway for 3+ VPCs — simpler than peering mesh, central routing. The first one — "Use VPC Reachability Analyzer — verifies connectivity before deploying" — should be a team default baked into your IaC templates.

How do I control cost and avoid bill surprises with AWS VPC Networking?

Three ways to prevent overspend: (1) tag every resource with env/team and enable billing alarms; (2) set budget thresholds to trigger Slack/email alerts; (3) review idle resources in Cost Explorer regularly and clean them up. Most AWS VPC Networking options offer a free tier — validate within free quota before scaling.