We are going to design the 4-Tier Azure Virtual Network here

1. Azure Virtual Network
2. WebTier Subnet + WebTier Network Security Group (Ports 80, 443)
3. AppTier Subnet + AppTier Network Security Group (Ports 8080, 80, 443)
4. DBTier Subnet + DBTier Network Security Group (Ports 3306, 1433, 5432)
5. Bastion Subnet + Bastion Network Security Group (Ports 80, 3389)
6. Terraform for_each Meta-Argument

1. azurerm_resource_group
2. azurerm_virtual_network
3. azurerm_subnet
4. azurerm_network_security_group
5. azurerm_subnet_network_security_group_association
6. azurerm_network_security_rule

Create the providers.tf file and add the providers.

Create the variables.tf file and define

• Business division
• Environment
• Resource group name
• Resource group location

Create the locals.tf file to define local values in Terraform

Create random-resources.tf file and define myrandom block

Create resource-groups.tf file with the resource group.

1. Virtual network, subnets, and subnet NSGs variables
2. Virtual Network
3. Subnets and subnet NSGs modules
4. Web, App, DB, Bastion Subnets associated with the Network Security Groups
5. Terraform Output Values for Azure Virtual Network

Create vnet-subnets-nsgs-variables.tf file and define

• Virtual Network name
• Virtual Network address_space
• Virtual Network Web Subnet Name
• Virtual Network Web Subnet Address Spaces
• Virtual Network Web Subnet NSG inbound ports map
• Virtual Network App Subnet Name
• Virtual Network App Subnet Address Spaces
• Virtual Network App Subnet NSG inbound ports map
• Virtual Network Database Subnet Name
• Virtual Network Database Subnet Address Spaces
• Virtual Network Database Subnet NSG inbound ports map
• Virtual Network Bastion Subnet Name
• Virtual Network Bastion Subnet Address Spaces
• Virtual Network Bastion Subnet NSG inbound ports map

Create vnet.tf file and the Virtual Network

1. Create \modules\subnets-nsgs directory and create main.tf inside it. Create the subnet and NSGs in it.
2. Create variables.tf file in the module directory and fill it with the variables.
   • Name of the subnet
   • Resource group name
   • Virtual network name
   • Subnet Address Spaces
   • Resource group location
   • NSG rule priorities and ports
3. Create outputs.tf file in the module directory and output
   • Subnet name
   • Subnet ID

Create subnets-nsgs.tf file and create modules for

• Web subnet
• App subnet
• DB subnet
• Bastion subnet

Create outputs.tf file and output the names and IDs of VNet and subnets.

# Terraform Initialize
terraform init

# Terraform Validate
terraform validate

# Terraform Plan
terraform plan

# Terraform Apply
terraform apply -auto-approve

1. Azure Resource Group
2. Azure Virtual Network
3. Azure Subnets (Web, App, DB, Bastion)
4. Azure Network Security Groups (Web, App, DB, Bastion)
5. View the topology
6. Verify Terraform Outputs in Terraform CLI

# Delete Resources
terraform destroy
terraform apply -destroy

# Clean-Up Files
rm -rf .terraform*
rm -rf terraform.tfstate*