Build Azure Route Tables with Terraform

Quick summary

Before going deeper, here is the simplest way to think about Azure Route Tables Terraform.

Why use Terraform for Azure Route Tables?

Route tables can be created manually in the Azure portal, but Terraform is better when you need standardization, reviewable routing logic, repeatable deployments, and consistent multi-environment infrastructure.

• It keeps routing logic in code instead of clicks.
• It makes route changes visible in Git and code review.
• It reduces manual mistakes with prefixes and next hop settings.
• It helps platform teams deploy consistent routing patterns across environments.
• It fits naturally into CI/CD and reusable networking modules.

Terraform code

This example creates:

• an Azure resource group
• one Azure Route Table
• two custom routes inside that route table

terraform {
  required_version = ">= 1.5.0"

  required_providers {
    azurerm = {
      source  = "hashicorp/azurerm"
      version = "~> 3.100"
    }
  }
}

provider "azurerm" {
  features {}
}

resource "azurerm_resource_group" "network_rg" {
  name     = var.resource_group_name
  location = var.location
}

resource "azurerm_route_table" "app_routes" {
  name                = var.route_table_name
  location            = azurerm_resource_group.network_rg.location
  resource_group_name = azurerm_resource_group.network_rg.name

  tags = {
    environment = var.environment
    managed_by  = "terraform"
    purpose     = "routing-control"
  }
}

resource "azurerm_route" "default_to_firewall" {
  name                   = "default-to-firewall"
  resource_group_name    = azurerm_resource_group.network_rg.name
  route_table_name       = azurerm_route_table.app_routes.name
  address_prefix         = "0.0.0.0/0"
  next_hop_type          = "VirtualAppliance"
  next_hop_in_ip_address = "10.20.0.4"
}

resource "azurerm_route" "onprem_via_gateway" {
  name                = "onprem-via-gateway"
  resource_group_name = azurerm_resource_group.network_rg.name
  route_table_name    = azurerm_route_table.app_routes.name
  address_prefix      = "172.16.0.0/16"
  next_hop_type       = "VirtualNetworkGateway"
}

Code breakdown

Terraform block

This defines the Terraform version and AzureRM provider version. Provider version pinning helps avoid unexpected changes during later deployments.

Provider block

The AzureRM provider is what Terraform uses to communicate with Azure and manage resources.

Resource group

Azure resources need a resource group, so this is usually one of the first resources created.

Route table resource

The azurerm_route_table resource creates the route table container itself. The actual traffic direction behavior comes from the routes placed inside it.

Route resources

The azurerm_route resources define the destination prefix and the next hop Azure should use for matching traffic.

Important route fields in Terraform

A good Azure Route Tables Terraform page should explain that routes are really traffic-matching instructions, not just named entries.

Next hop types explained

The next hop type is one of the most important parts of route design because it tells Azure what to do with matching traffic.

Suggested variables file

Variables make Route Table Terraform code more reusable across development, testing, and production environments.

variable "resource_group_name" {
  description = "Name of the Azure resource group"
  type        = string
}

variable "location" {
  description = "Azure region for deployment"
  type        = string
  default     = "South Africa North"
}

variable "route_table_name" {
  description = "Name of the Azure Route Table"
  type        = string
}

variable "environment" {
  description = "Environment name"
  type        = string
  default     = "dev"
}

Example terraform.tfvars

resource_group_name = "rg-network-dev-san-1"
location            = "South Africa North"
route_table_name    = "rt-app-dev-san-1"
environment         = "dev"

Suggested outputs

Outputs help expose route table IDs and names so they can be used by subnet association resources or downstream modules.

output "route_table_name" {
  value = azurerm_route_table.app_routes.name
}

output "route_table_id" {
  value = azurerm_route_table.app_routes.id
}

How to run it

A simple Terraform execution flow looks like this:

terraform init
terraform fmt
terraform validate
terraform plan
terraform apply

In real teams, these steps often run through CI/CD after review rather than manually every time.

Real-world usage

This Route Table Terraform pattern can grow naturally into real enterprise routing workflows.

Forced tunneling through firewall

A team uses a default route with next hop type VirtualAppliance so all outbound traffic from a subnet is inspected by a central firewall.

Hybrid routing to on-premises

Traffic destined for datacenter ranges is sent through a virtual network gateway instead of following internet-facing paths.

Hub-and-spoke network design

Spoke subnet route tables direct traffic toward centralized services in the hub for control, logging, or inspection.

Best practices

• Use clear route table and route names.
• Keep destination prefixes specific and intentional.
• Understand exactly why each next hop is chosen.
• Document route purpose, not just the route itself.
• Test route logic in non-production before broad rollout.
• Be very careful with default routes like 0.0.0.0/0.
• Keep route design aligned with subnet and security architecture.
• Separate routing logic from traffic filtering logic in your thinking and code.

Common mistakes

• Using the wrong address prefix so the route never matches.
• Choosing the wrong next hop type for the design.
• Forgetting to associate the route table with the intended subnet.
• Using default routes too broadly without understanding the impact.
• Assuming route tables filter traffic like NSGs do.
• Hardcoding values without variables in reusable environments.

Summary

Azure Route Tables Terraform is one of the best practical ways to understand how Azure traffic direction becomes infrastructure as code. It teaches you how custom routes are expressed, how prefixes and next hops interact, and how reusable routing foundations are built in real Azure environments.

Official Azure documentation

These official references are useful if you want deeper platform details for Azure Route Tables and the Terraform resources used to create them.

• Create, change, or delete a route table
• User-defined routes overview
• Terraform AzureRM route table resource
• Terraform AzureRM route resource
• Diagnose a virtual machine routing problem