main.tf

resource "google_compute_instance" "vm_instance" {
    name = "${var.instance_name}"
    zone = "${var.instance_zone}"
    machine_type = "${var.instance_type}"

    boot_disk {
        initialize_params {
            image = "debian-cloud/debian11"
        }
    }

    network_interface {
        network = "${var.instance_network}"
        access_config {
            # ALlocate a one-to-one NAT IP to the instance
        }
    }
}

mynetwork.tf

# Create the mynetwork network
resource "google_compute_network" "mynetwork" {
  name = "mynetwork"
  # RESOURCE properties would be here
  auto_create_subnetworks = "true"
}

# Add a firewall rule to allow HTTP, SSH, RDP and ICMP traffic
resource "google_compute_firewall" "mynetwork-allow-http-ssh-rdp-icmp" {
  name    = "mynetwork-allow-http-ssh-rdp-icmp"
  network = google_compute_network.mynetwork.self_link
  allow {
    protocol = "tcp"
    ports    = ["22", "80", "3389"]
  }
  allow {
    protocol = "icmp"
  }
  source_ranges = ["0.0.0.0/0"]
}

# Create the mynet-us-vm instance
module "mynet-us-vm" {
  source           = "./instance"
  instance_name    = "mynet-us-vm"
  instance_zone    = "us-central1-b"
  instance_network = google_compute_network.mynetwork.self_link
}

# Create the mynet-eu-vm" instance
module "mynet-eu-vm" {
  source           = "./instance"
  instance_name    = "mynet-eu-vm"
  instance_zone    = "europe-central2-b"
  instance_network = google_compute_network.mynetwork.self_link
}

network.tf

# Configuring Firewall Rules using Terraform - Preparing for GCP Certification

# Create the mynetwork network
resource "google_compute_network" "mynetwork" {
    name = "mynetwork"
    # RESOURCE properties would be here
    auto_create_subnetworks = "true"
}

# Add a firewall rule to allow HTTP, SSH, RDP and ICMP traffic
resource "google_compute_firewall" "mynetwork-allow-http-ssh-rdp-icmp"{
    name = "mynetwork-allow-http-ssh-rdp-icmp"
    network = google_compute_network.mynetwork.self_link
    allow {
        protocol = "tcp"
        ports = ["22", "80", "3389"]
    }
    allow {
        protocol = "icmp"
    }
    source_ranges = ["0.0.0.0/0"]
}