FortiGate Firewall High Availability on AWS

The problem

A single firewall instance is a single point of failure. If it goes down, so does every workload behind it — which isn't acceptable for a production perimeter.

The approach

This project deploys FortiGate-VM in an active-passive HA pair across two Availability Zones within one VPC, so a zone-level failure doesn't take the whole perimeter down with it.

Infrastructure is fully defined in Terraform:

# Simplified shape of the HA pair — see the repo for the full module
resource "aws_instance" "fortigate_primary" {
  availability_zone = "us-east-1a"
  # ...
}

resource "aws_instance" "fortigate_secondary" {
  availability_zone = "us-east-1b"
  # ...
}

Key components:

• VPC & subnets spanning both AZs
• Elastic IPs for stable public-facing addressing during failover
• IAM roles scoped to exactly what the FortiGate instances need
• Security groups enforcing least-privilege traffic rules

Outcome

Rapid failover between AZs with no manual intervention, and a fully reproducible deployment — tear it down and rebuild it identically from terraform apply.