PNETLab on Google Cloud – Part 1: Server Deployment

Wed, 26 Mar 2025 13:27:29 +0700

Introduction

While running GNS3 inside Orbstack, I encountered an issue with Orbstack’s networking system that prevented my localhost from communicating with GNS3 appliances. Instead of spending more time troubleshooting something that is limited by its design, I decided to deploy a cloud-hosted network lab using PNETLab.

The lab infrastructure is provisioned using Terraform and remote access to the lab is secured through Tailscale instead of exposing it directly to the Internet.

This article covers the deployment process. The remote access setup will be covered in a separate article.

Goals

Build reusable PNETLab server with Terraform.

Prerequisites

GCP & Tailscale accounts.
GCP CLI installed.
Terraform installed.

Architecture Overview

Here’s an overview of what we’re going to build:

The setup consists of:

Terraform for infrastructure automation.
A GCP compute instance running PNETLab.
A private VPC network.
Cloud Router for outbound internet access (dynamic IP).
Tailscale for secure remote access to PNETLab instance

Prepare the GCP Environment

Before we begin, several prerequisites need to be prepared within Google Cloud Platform.

Note: I’m using GCP’s free trial credits for this setup, if you’re on a paid account, the steps remain the same.

GCP Authentication

Terraforms requires credentials to access your Google Cloud resources. There are several methods for this but I will be using Application Default Credentials (ADC) method for this personal project.

From CLI, run the following:

$ gcloud auth application-default login

A browser window will pop ups, requesting for Google account authentication. After a successful authtentication, the credentials will be stored in the default location and Terraform will look into it automatically.

Creating a GCP Project

First, create a new project for our PNETLab deployment using GCP CLI.

$ PROJECT_ID=pnetlab-$RANDOM
$ echo $PROJECT_ID
pnetlab-xxx
$ mkdir $PROJECT_ID
$ cd $PROJECT_ID
$ gcloud projects create $PROJECT_ID
$ gcloud config set project $PROJECT_ID

Then, link the project to your billing account.

$ gcloud billing accounts list              
ACCOUNT_ID            NAME                OPEN  MASTER_ACCOUNT_ID
AAAAAA-BBBBBB-CCCCCC  My Billing Account  True
$ gcloud billing projects link $PROJECT_ID --billing-account=AAAAAA-BBBBBB-CCCCCC

Enabling Compute Engine API

To allow Terraform to manage VM resources, we must enable the Compute Engine API.

$ gcloud services enable compute.googleapis.com

Server Deployment with Terraform

We will use Terraform to provision our server that will host PNETLab.

Preparing Project Structure

We’ll use the following folder structure.

$ tree
.
├── README.MD
└── terraform
    ├── terraforms.tfvars # sensitive informations goes here (project_id, region, user/keys)
    ├── main.tf # defined gcp resources
    └── variables.tf

1 directories, 4 files

terraform.tfvars

terraforms.tfvars contains the following:

project_id      = ""
region          = ""
zone            = ""
os_image        = "projects/ubuntu-os-cloud/global/images/ubuntu-1804-bionic-v20240116a"

Other than os_image, make your adjustment.

main.tf

main.tf file contains the following:

terraform {
  required_providers {
    google = {
      source = "hashicorp/google"
    version = "~> 4.5" }
  }
}

provider "google" {
  project = var.project_id
  region  = var.region
  zone    = var.zone
}

# SETUP NETWORK #
resource "google_compute_network" "pnetlab_vpc" {
  name                    = "pnetlab-vpc"
  auto_create_subnetworks = false
}

resource "google_compute_subnetwork" "pnetlab_subnet" {
  name          = "pnetlab-subnet"
  network       = google_compute_network.pnetlab_vpc.id
  ip_cidr_range = "10.10.1.0/24"
}

resource "google_compute_firewall" "allow_ssh_access" {
  name    = "allow-ssh"
  network = google_compute_network.pnetlab_vpc.id

  allow {
    protocol = "tcp"
    ports    = ["22"]
  }

  source_ranges = [ "0.0.0.0/0" ]
}

# NAT
resource "google_compute_router" "pnetlab_router" {
  name = "pnetlab-router"
  region = var.region
  network = google_compute_network.pnetlab_vpc.id

}

resource "google_compute_router_nat" "pnetlab_router_nat" {
  name = "pnetlab-router-nat"
  region = var.region
  router = google_compute_router.pnetlab_router.name
  nat_ip_allocate_option = "AUTO_ONLY" # use dynamic public ip for nat
  source_subnetwork_ip_ranges_to_nat = "ALL_SUBNETWORKS_ALL_IP_RANGES" # nat any sources ip range available within the vpc

}

# SETUP EXT DISK #
resource "google_compute_disk" "additional_disk" {
  name   = "pnetlab-additional-disk"
  type   = "pd-standard"  # Choose disk type (pd-standard, pd-ssd, etc.)
  size = 50 
  lifecycle {
    prevent_destroy = true
  }
}

# SETUP INSTANCES #
# ubuntu-1804-bionic-v20240116a                                 ubuntu-os-cloud      ubuntu-1804-lts
resource "google_compute_instance" "pnetlab_server" {
  name         = "pnetlab-server"
  machine_type = "n2-standard-2"
  tags         = ["pnetlab"]

  boot_disk {
    initialize_params {
      image = var.os_image # cloud image
      size  = 20                 # assign 20gb
      type  = "pd-standard"
    }
  }
  
  # external disk 50gb
  attached_disk {
    source = google_compute_disk.additional_disk.id
  }

  network_interface {
    network    = google_compute_network.pnetlab_vpc.id
    subnetwork = google_compute_subnetwork.pnetlab_subnet.id

    # Disable public IP
    # access_config {
    #  network_tier = "STANDARD"
    # }
  }

  scheduling {
    automatic_restart           = true
    on_host_maintenance         = "MIGRATE"
    preemptible                 = false
    provisioning_model          = "STANDARD"
  }

  advanced_machine_features {
    enable_nested_virtualization = true
  }
  
}

This configuration provisions:

Custom VPC network.
Subnet.
Firewall rules.
Cloud NAT router.
Additional persistent disk.
Enabled nested virtualization (need machine type that support nested virtualization).

There’s also n1 for alternative machine type if you worry about the cost, lets say n1-custom-1-2048, which means machine type is n1 with single core and 2 GB of RAM.

variables.tf

variables.tf define the variables we used in the tfvars file, it contains:

variable "project_id" {
  type        = string
  description = "Project ID"
}

variable "region" {
  type        = string
  description = "Project region"
  default     = "us-central"
}

variable "zone" {
  type        = string
  description = "Project zone"
  default     = "us-central1-a"
}

variable "os_image" {
  type        = string
  description = "OS family"
}

VM Deployment

Within the terraform folder, initialize the terraform working directory.

$ terraform init

The init step only needs to be performed be performed during the first deployment or after provider/module changes.

With all the resource files defined, we can start the deployment.

$ terraform fmt         # Format your Terraform files  
$ terraform validate    # Check for syntax errors  
$ terraform plan -out pnetlab-deploy       #Preview the infrastructure changes  
$ terraform apply pnetlab-deploy  # Deploy the resources

Verify Deployment

After it finishes, check if the instance is running:

$ gcloud compute instances list --filter="name=pnetlab-server" --project="$PROJECT_ID"

Please mind that the terraform config I provide here is only reusable for personal project, it’s not reusable for team scale project.

PNETLab Installation

Install PNETLab

SSH into the instance using gcloud cli.

$ gcloud compute ssh INSTANCE_NAME --zone=YOUR_ZONE

Add pnetlab repository with the following command.

$ echo "deb [trusted=yes] http://repo.pnetlab.com ./" | sudo tee -a /etc/apt/sources.list

Update the repository and install pnetlab.

$ sudo apt-get update
$ sudo apt-get install pnetlab

During installation process, you might be asked to replace kernel configuration like this

Just go with it and continue the installation.

Once it finished, you will have a name resolution/DNS issue, but that’s fine for now.

Server Configuration

Swap

Create a swap disk, allocate the size according to your need.

$ sudo fallocate -l 1G /swapfile
$ sudo chmod 600 /swapfile
$ sudo mkswap /swapfile
$ sudo swapon /swapfile
$ sudo cp /etc/fstab{,.bak}
$ sudo '/swapfile none swap sw 0 0' | sudo tee -a /etc/fstab

DNS

Edit file /etc/network/interfaces add line dns-nameservers 8.8.8.8 to the configuration of interface pnet0.

...
# The primary network interface
iface eth0 inet manual
auto pnet0
iface pnet0 inet dhcp
    dns-nameservers 8.8.8.8	
    bridge_ports eth0
    bridge_stp off
...

And restart the networking service.

$ sudo service networking restart

Disk

Time to add the additional disk we defined in the terraform resource. The purpose of this disk is to store all the pnetlab project files as well as the images later. We can preserve the lab data in this disk in case the VM need to be replaced/gone wrong, we will get into the detail later.

In my case, the additional disk is available at /dev/sdb.

$ sudo lsblk
NAME    MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
loop0     7:0    0 40.4M  1 loop /snap/snapd/20671
loop1     7:1    0  368M  1 loop /snap/google-cloud-cli/203
loop2     7:2    0 63.9M  1 loop /snap/core20/2105
sda       8:0    0   20G  0 disk 
├─sda1    8:1    0 19.9G  0 part /
├─sda14   8:14   0    4M  0 part 
└─sda15   8:15   0  106M  0 part /boot/efi
sdb       8:16   0  100G  0 disk

We’ll create an LVM disk out of it.

$ sudo vgcreate /dev/vg01 /dev/sdb
  Volume group "vg01" successfully created
$ sudo lvcreate -l 100%FREE --name lv01 vg01 
  Logical volume "lv01" created.
$ sudo mkfs.ext4 /dev/vg01/lv01 
mke2fs 1.44.1 (24-Mar-2018)
Discarding device blocks: done                            
Creating filesystem with 26213376 4k blocks and 6553600 inodes
Filesystem UUID: f1173542-f07c-493f-89e6-188439880465
Superblock backups stored on blocks: 
  32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208, 
  4096000, 7962624, 11239424, 20480000, 23887872

Allocating group tables: done                            
Writing inode tables: done                            
Creating journal (131072 blocks): done
Writing superblocks and filesystem accounting information: done

Then we set a mount point for the volume we just created at /mnt/unetlab

$ sudo mkdir /mnt/unetlab
$ sudo mount /dev/vg01/lv01 /mnt/unetlab

Edit the /etc/fstab file and add the following line to mount /mnt/unetlab on boot:

/dev/vg01/lv01  /mnt/unetlab  ext4  defaults  0  0

Now we’ll create a new directory for PNETLab project files and image files in our newly mounted disk.

$ sudo mkdir /mnt/unetlab/addons
$ sudo mkdir /mnt/unetlab/labs

Next, we’ll remove the old directories for project files and image files, and replace them with symbolic links pointing to the new directories on the mounted disk.

$ sudo rm -rf /opt/unetlab/addons/ 
$ sudo rm  -rf /opt/unetlab/labs/
$ sudo ln -s /mnt/unetlab/addons/ /opt/unetlab/
$ sudo ln -s /mnt/unetlab/labs/ /opt/unetlab/

Change ownership of the new labs directory to ensure PNETLab’s services can access it back.

$ sudo chown -R www-data:www-data /mnt/unetlab/labs/

Grub

Remove the default grub config.

$ sudo rm /etc/default/grub.d/50-cloudimg-settings.cfg
$ sudo update-grub

Restart Server

To complete the installation, restart the server.

$ sudo reboot

Once you logged in, there will be a pop up asking for setting root password, hostname, and NTP. Configure these according to your preferences.

We also need to make sure that the internet connectivity is working with simple ping check to 1.1.1.1.

Verify Installation

Since the server configured without a public IP address, the PNETLab web interface cannot be accessed directly from the internet. The installation can be validated locally using curl from the server.

$ curl -k https://localhost

Expected output:

HTTP/1.1 301 Moved Permanently
Date: Thu, 28 May 2026 15:02:55 GMT
Server: Apache/2.4.29 (Ubuntu)
Access-Control-Allow-Origin: *
Access-Control-Allow-Headers: *
Location: /store/public/admin/main/view
...

Update Version (Optional)

After the installation completed, we can directly upgrade PNETLab to the latest version. It’s an optional, so I will just put the official guide link on how to upgrade the lab version: go here.

Troubleshoot

I know things that may go wrong before you finish it, so there are a few problems I encountered and the solutions.

Cannot install packages

Try disable/comment this whole url line from the repository.

#deb [trusted=yes] http://i-share.top/repo ./
#deb [trusted=yes] http://repo.pnetlab.com ./

Cloud Appliance: DHCP not working

Verify udhcpd service is running and enabled.

$ service udhcpd status
$ cat /etc/default/udhcpd | grep ENABLED

Set to enabled and restart to see if it’s working.

Conclusion

We have completed the deployment process of PNETLab server on Google Cloud using Terraform. At this stage, the lab is running internally but remains inaccessible from outside the private network.

In the next article, we will configure Tailscale to provide secure remote access to the lab.

Deploying PNETLab on GCP With Terraform and Tailscale on Ef's log