Multiple subnets in same VNet with Terrafrom - azure

Question

I'm completely new to terraform and I'm trying to learn and write a TF code to automate Azure VM deployment. I'm trying to cover each parts as modules (except rg) rather than keeping it in a single main.tf file.
My intention is to create 1 vnet (TESTVNET) and create multiple subnets in same Vnet, where I can define the subnet name and address in my tfvars file.
I'm able to reach till creation on VNet, but cant loop through the defined subnets
Please go through my code. File Main.tf
resource "azurerm_resource_group" "resource_group" {
name = var.RGname
location = var.RGlocation
}
module "VNET" {
source = "./Modules/NetworkConfig"
name = var.VNETname
address_space = var.address_space
location = var.RGlocation
resource_group_name = azurerm_resource_group.resource_group.name
}
module "SUBNETS" {
source = "./Modules/SubnetConfig"
Subnetlist = var.Subnetlist
virtual_network_name = module.VNET.vnet_name
resource_group_name = azurerm_resource_group.resource_group.name
depends_on = [azurerm_resource_group.resource_group, module.VNET.vnet]
}
Variables.tf (of main)
variable "RGlocation" {
}
variable "RGname" {
}
variable "VNETname" {
}
variable "address_space" {
}
variable "Subnetlist" {
type = map(object({
name = list(string)
address = list(string)
}))
}
File main.tfvars
RGlocation = "westus"
RGname = "TEST-RG1"
VNETname = "TEST-VNET-01"
address_space = "10.0.0.0/16"
Subnetlist = {
"list" = {
name = ["TESTSUBNET","TESTSUBNET1","TESTSUBNET2"]
address = ["10.0.1.0/24","10.0.2.0/24","10.0.3.0/24"]
}
}
File Subnets.tf (module)
resource "azurerm_subnet" "SUBNETS" {
for_each=var.Subnetlist
name=each.value.name
address_prefixes=each.value.address
resource_group_name = var.resource_group_name
virtual_network_name = var.virtual_network_name
}
File variable.tf (subnet module)
variable "resource_group_name" {
}
variable "virtual_network_name" {
}
variable "Subnetlist" {
type = map(object({
name = list(string)
address = list(string)
}))
}
Below if the error that I'm getting
╷
│ Error: Incorrect attribute value type
│
│ on Modules\SubnetConfig\Subnet.tf line 3, in resource "azurerm_subnet" "SUBNETS":
│ 3: name=each.value.name
│ ├────────────────
│ │ each.value.name is list of string with 3 elements
│
│ Inappropriate value for attribute "name": string required.
Could anyone please tell me how to resolve it? Also, please do let me know if this is not the right approach.

Answer 1

The way you iterate over Subnetlist is incorrect - you only get the value of "list" key, ending up with a bundle of subnets instead of individual items. Make it a map of individual subnet objects instead:
variable "Subnetlist" {
type = map(object({
name = string
address = string
}))
}
Then pass it in tfvars like:
Subnetlist = {
"s1" = { name = "TESTSUBNET", address = "10.0.1.0/24" },
"s2" = { name = "TESTSUBNET1", address = "10.0.2.0/24" },
"s3" = { name = "TESTSUBNET2", address = "10.0.3.0/24" }
}
Finally consume it in the module like this:
resource "azurerm_subnet" "SUBNETS" {
for_each = var.Subnetlist
name = each.value.name
address_prefixes = each.value.address
resource_group_name = var.resource_group_name
virtual_network_name = var.virtual_network_name
}