Using the resource ID from a for_each resource block - azure

Question

I've created a Terraform template that creates 2 route tables and 2 subnets using the for_each command. I am trying to associate the route tables to the two subnets, however I am struggling to do so because I don't know how to obtain the ID for the route tables and subnets as the details are not in a variable, and I'm not sure how to get that information and use it. Please may someone provide assistance?
Thank you
Main Template
# SUBNETS DEPLOYMENT
resource "azurerm_subnet" "subnets" {
depends_on = [azurerm_virtual_network.vnet]
for_each = var.subnets
resource_group_name = var.rg.name
virtual_network_name = var.vnet.config.name
name = each.value.subnet_name
address_prefixes = each.value.address_prefixes
}
# ROUTE TABLE DEPLOYMENT
resource "azurerm_route_table" "rt" {
depends_on = [azurerm_virtual_network.vnet]
for_each = var.rt
name = each.value.route_table_name
resource_group_name = var.rg.name
location = var.rg.location
disable_bgp_route_propagation = true
route = [ {
address_prefix = each.value.address_prefix
name = each.value.route_name
next_hop_in_ip_address = each.value.next_hop_ip
next_hop_type = each.value.next_hop_type
} ]
}
# ROUTE TABLE ASSOICATION
resource "azurerm_subnet_route_table_association" "rt_assoication" {
subnet_id = azurerm_subnet.subnets.id
route_table_id = azurerm_route_table.rt.id
}
Variables
# SUBNET VARIBALES
variable "subnets" {
description = "subnet names and address prefixes"
type = map(any)
default = {
subnet1 = {
subnet_name = "snet-001"
address_prefixes = ["172.17.208.0/28"]
}
subnet2 = {
subnet_name = "snet-002"
address_prefixes = ["172.17.208.32/27"]
}
}
}
# ROUTE TABLES VARIABLES
variable "rt" {
description = "variable for route tables."
type = map(any)
default = {
rt1 = {
route_table_name = "rt1"
address_prefix = "0.0.0.0/0"
route_name = "udr-azure-firewall"
next_hop_ip = "10.0.0.0"
next_hop_type = "VirtualAppliance"
}
rt2 = {
route_table_name = "rt2"
address_prefix = "0.0.0.0/0"
route_name = "udr-azure-firewall"
next_hop_ip = "10.0.0.0"
next_hop_type = "VirtualAppliance"
}
}
}
The error I get when I run terraform plan is:
│ Error: Missing resource instance key
│
│ on modules\vnet\main.tf line 74, in resource "azurerm_subnet_route_table_association" "rt_assoication":
│ 74: subnet_id = azurerm_subnet.subnets.id
│
│ Because azurerm_subnet.subnets has "for_each" set, its attributes must be accessed on specific instances.
│
│ For example, to correlate with indices of a referring resource, use:
│ azurerm_subnet.subnets[each.key]
╵
╷
│ Error: Missing resource instance key
│
│ on modules\vnet\main.tf line 75, in resource "azurerm_subnet_route_table_association" "rt_assoication":
│ 75: route_table_id = azurerm_route_table.rt.id
│
│ Because azurerm_route_table.rt has "for_each" set, its attributes must be accessed on specific instances.
│
│ For example, to correlate with indices of a referring resource, use:
│ azurerm_route_table.rt[each.key]

Answer 1

Looks like you are almost there, update the following in the subnet-route table association block, it should work:
# ROUTE TABLE ASSOICATION
resource "azurerm_subnet_route_table_association" "rt_assoication" {
subnet_id = azurerm_subnet.subnets[each.key].id
route_table_id = azurerm_route_table.rt[each.key].id
}