GCP google compute instance from machine image override ip how

How to override the ip address in a machine image? Is this a bug?

terraform plan works
terraform apply yields 6 error messages of the same:

Error: Error creating network interfaces: exactly one of network or subnetwork must be provided

resource “google_compute_instance_from_machine_image” “cassandra_node” {
project = var.project
provider = google-beta
zone = var.zone

  count    = 6
  name     = local.cassandra_settings[count.index].name 

  source_machine_image = join("",["projects/",var.project,"/global/machineImages/cassandra-node"])

  network_interface  {
     network_ip = local.cassandra_settings[count.index].ip