How to use existing resources from another resource group to make deployments in new resource group using Terraform

Question

I want to create resources in a new resource group but i want to use a virtual network for those resources which is in another resource group. How do i do this? For example, i want to create redis/postgresql in resourcegroupA but i want to make use of the virtual network which is in resourcegroupB. Is it possible?

This is the resource group from where i am retrieving the vnet-

    resource "azurerm_resource_group" "azresourcegroup" {
      name        = 
      "resourcegroupA"
      location    = var.resource_group_location
    }

    #-----CREATING VIRTUAL NETWORK-----

    resource "azurerm_virtual_network" "vnet2" {
       name                = "virtualnetworkA"
       location            = azurerm_resource_group.azresourcegroup.location
       resource_group_name = azurerm_resource_group.azresourcegroup.name
       address_space       = [var.virtual_network_address_prefix_infra,var.virtual_network_address_prefix]

I retrieved it while using it for another resource group like this-

    data "azurerm_resource_group" "azresourcegroup" {
      name        = "resoucegroupA"
    }

    data "azurerm_virtual_network" "vnet2" {
     name                = "virtualnetworkA"
      resource_group_name = data.azurerm_resource_group.azresourcegroup.name
    }

I want to use the above virtual network but want to create the other resources in the new resource group which is-

     resource "azurerm_resource_group" "main" {
      name        = "resourcegroupB"
      location    = var.resource_group_location
    }

I am making use of module to create redis cache that requires the vnet which is created in other RG-

    module "rediscache" {
      source                             = "../../modules/rediscache"
      prefix                             = var.prefix
      environmentType                    = var.environmentType
      virtual_network_name               = var.virtual_network_name
      unique_identifier                  = var.unique_identifier_kube
      resource_group_name                = azurerm_resource_group.main.name
      resource_group_location            = var.resource_group_location
      redis_subnet_address_prefix        = var.redis_subnet_address_prefix
      azurerm_virtual_network_name       = data.azurerm_virtual_network.vnet2.name
      azurerm_log_analytics_workspace_id = azurerm_log_analytics_workspace.workspace.id
    }

To simplify this, vnet is created in other resource group and redis in another one.But i want to use that vnet. also if i change the resource group name argument used in module, from azurerm_resource_group.main.name to data.azurerm_resource_group.azresourcegroup.name then it creates the redis in the 1st resource group which i dont want. Please help.

Answer 1

Of course, it's possible. The only condition is that the virtual network should be in the same location. Then you can quote it in the Terraform code via the Terraform Data Source azurerm_virtual_network like this:

data "azurerm_virtual_network" "example" {
  name                = "production"
  resource_group_name = "networking"
}