Enterprise AWS Network Baseline with Terraform
Production-grade AWS network infrastructure deployed via Terraform including VPC, Transit Gateway, Route53, and security groups following AWS best practices.
DevOps Cloud Engineer Platform Engineer
Terraform AWS VPC Transit Gateway Network Firewall NAT Gateway VPC Flow Logs AWS Config PrivateLink CloudWatch Route53 Resolver
The Problem
Our organization operated 30+ AWS accounts with inconsistent network configurations, creating security vulnerabilities and operational chaos. Each development team had created their own VPCs with overlapping CIDR ranges, making inter-account communication impossible. We had no centralized egress control, allowing direct internet access from all subnets, violating PCI-DSS requirements. Network ACLs were rarely configured, security groups had overly permissive 0.0.0.0/0 rules, and there was zero network segmentation between application tiers. AWS Transit Gateway wasn't utilized, forcing complex VPC peering meshes. Cloud costs were inflated due to data transfer across poorly designed networks, and we failed two compliance audits due to network security gaps.
The Solution
**Network Architecture Design**: Architected a hub-and-spoke topology using AWS Transit Gateway as the central routing hub. Designed a standardized CIDR allocation strategy using /16 VPCs with non-overlapping RFC 1918 ranges. Created three-tier subnet architecture: public subnets (DMZ), private subnets (application tier), and isolated subnets (database tier) across three availability zones for high availability.
**Infrastructure as Code**: Built Terraform modules for repeatable VPC provisioning with embedded security best practices. Created reusable modules for NAT Gateways (one per AZ for redundancy), Internet Gateways, route tables, and Transit Gateway attachments. Implemented AWS Network Firewall for centralized traffic inspection and threat detection.
**Security Hardening**: Configured Network ACLs as an additional defense layer with explicit deny rules for known malicious IPs. Implemented AWS PrivateLink for secure access to AWS services without internet exposure. Set up VPC Flow Logs streaming to S3 and analyzed with CloudWatch Insights for anomaly detection.
**Cost Optimization**: Eliminated unnecessary cross-AZ traffic reducing data transfer costs by 30%. Consolidated internet egress through centralized NAT Gateways in a shared services VPC. Implemented VPC endpoints for S3 and DynamoDB to avoid NAT Gateway charges.
**Infrastructure as Code**: Built Terraform modules for repeatable VPC provisioning with embedded security best practices. Created reusable modules for NAT Gateways (one per AZ for redundancy), Internet Gateways, route tables, and Transit Gateway attachments. Implemented AWS Network Firewall for centralized traffic inspection and threat detection.
**Security Hardening**: Configured Network ACLs as an additional defense layer with explicit deny rules for known malicious IPs. Implemented AWS PrivateLink for secure access to AWS services without internet exposure. Set up VPC Flow Logs streaming to S3 and analyzed with CloudWatch Insights for anomaly detection.
**Cost Optimization**: Eliminated unnecessary cross-AZ traffic reducing data transfer costs by 30%. Consolidated internet egress through centralized NAT Gateways in a shared services VPC. Implemented VPC endpoints for S3 and DynamoDB to avoid NAT Gateway charges.
Key Highlights
- Reduced monthly AWS networking costs by 30% ($12K savings)
- Achieved CIS AWS Foundations Benchmark Level 2 compliance
- Standardized network architecture across 30+ AWS accounts
- Eliminated 450+ overly permissive security group rules
- Reduced VPC provisioning time from 2 days to 15 minutes
- Implemented network segmentation isolating 15+ microservices by tier
- Configured centralized egress traffic inspection blocking 1,200+ threats monthly
- Passed PCI-DSS audit with zero network-related findings
- Created automated network compliance scanning with AWS Config
- Built disaster recovery capability with cross-region Transit Gateway peering
- Implemented IPv6 dual-stack support for future-proofing
- Established network documentation auto-generated from Terraform state
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