Infrastructure as Code with Terraform for Networking: A Practical Guide

Infrastructure as Code (IaC) with Terraform for networking: Cisco ACI, FortiGate, Palo Alto Panorama, and AWS/Azure/GCP providers. Declarative management using a state file. The ideal complement to Ansible for managing configuration drift. 2026 Terraform networking guide.

Why Use Terraform for Networking

• Declarative: describes the desired state, not the steps
• State file: tracks deployed resources
• Plan/Apply: preview changes before deployment
• Idempotent and safe
• Multi-cloud and on-premises management using the same language

Network Providers

• AWS/Azure/GCP: VPCs, subnets, and security groups
• Cisco ACI: tenants, EPGs, and contracts
• Panorama (Palo Alto): policies and devices
• FortiGate/FortiManager: address objects and policies
• Juniper Mist: sites, APs, and templates
• Meraki: organizations and networks

Project Structure

• main.tf: primary resources
• variables.tf: inputs
• outputs.tf: outputs
• terraform.tfvars: values (secrets stored in a vault)
• modules/: reusable modules

FortiGate Policy Example

• resource "fortios_firewall_policy" "allow_web" {
• policyid = 1
• name = "Allow-Web"
• srcintf { name = "port1" }
• dstintf { name = "port10" }
• srcaddr { name = "all" }
• dstaddr { name = "all" }
• service { name = "HTTP" }
• service { name = "HTTPS" }
• action = "accept"
• }

Workflow

• terraform init: download providers
• terraform plan: preview changes
• terraform apply: deploy resources
• terraform destroy: remove resources
• terraform state: manage state

State Backend

• Local (default): terraform.tfstate
• Remote: S3, Azure Storage, or Terraform Cloud
• Locking: DynamoDB prevents concurrent apply operations
• Versioning: history of state changes

Modules

• Reusable: a 'vpc' module for a standard AWS VPC
• Terraform Registry: 13000+ public modules
• Private registry: Terraform Cloud or GitHub

Terraform vs. Ansible for Networking

• Terraform: declarative, stateful, and designed for day 0/1 provisioning
• Ansible: procedural, stateless, and designed for day 2 operations
• Combined approach: Terraform for bootstrapping and Ansible for operations

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