aks_cluster_default_node_pool.tf

#create system node pool
    default_node_pool {
        name                  = substr(var.system_node_pool.name, 0, 12)
        orchestrator_version  = var.kubernetes_version
        node_count            = var.system_node_pool.node_count
        vm_size               = var.system_node_pool.vm_size
        type                  = "VirtualMachineScaleSets"
        availability_zones    = var.system_node_pool.zones
        max_pods              = 250
        os_disk_size_gb       = 128
        node_labels           = var.system_node_pool.labels
        node_taints           = var.system_node_pool.taints
        enable_auto_scaling   = var.system_node_pool.cluster_auto_scaling
        min_count             = var.system_node_pool.cluster_auto_scaling_min_count
        max_count             = var.system_node_pool.cluster_auto_scaling_max_count
        enable_node_public_ip = false
        #advanced networking
        vnet_subnet_id        = azurerm_subnet.aks_subnet.id
  }