A dual-stack embedded-etcd development k3s cluster (originally from this discussion: https://github.com/k3s-io/k3s/discussions/9807)

Vagrantfile.k3s-dev-cluster

# -*- mode: ruby -*-
# vi: set ft=ruby :

# All Vagrant configuration is done below. The "2" in Vagrant.configure
# configures the configuration version (we support older styles for
# backwards compatibility). Please don't change it unless you know what
# you're doing.
Vagrant.configure("2") do |config|
  # The most common configuration options are documented and commented below.
  # For a complete reference, please see the online documentation at
  # https://docs.vagrantup.com.

  # Every Vagrant development environment requires a box. You can search for
  # boxes at https://vagrantcloud.com/search.
  config.vm.box = "generic/ubuntu2204"
  config.vm.box_version = "4.3.12"

  # Disable automatic box update checking. If you disable this, then
  # boxes will only be checked for updates when the user runs
  # `vagrant box outdated`. This is not recommended.
  # config.vm.box_check_update = false

  # Create a forwarded port mapping which allows access to a specific port
  # within the machine from a port on the host machine. In the example below,
  # accessing "localhost:8080" will access port 80 on the guest machine.
  # NOTE: This will enable public access to the opened port
  # config.vm.network "forwarded_port", guest: 80, host: 8080

  # Create a forwarded port mapping which allows access to a specific port
  # within the machine from a port on the host machine and only allow access
  # via 127.0.0.1 to disable public access
  # config.vm.network "forwarded_port", guest: 80, host: 8080, host_ip: "127.0.0.1"

  # Create a private network, which allows host-only access to the machine
  # using a specific IP.
  # config.vm.network "private_network", ip: "192.168.33.10"

  # Create a public network, which generally matched to bridged network.
  # Bridged networks make the machine appear as another physical device on
  # your network.
  # config.vm.network "public_network"

  # Share an additional folder to the guest VM. The first argument is
  # the path on the host to the actual folder. The second argument is
  # the path on the guest to mount the folder. And the optional third
  # argument is a set of non-required options.
  # config.vm.synced_folder "../data", "/vagrant_data"

  # Disable the default share of the current code directory. Doing this
  # provides improved isolation between the vagrant box and your host
  # by making sure your Vagrantfile isn't accessible to the vagrant box.
  # If you use this you may want to enable additional shared subfolders as
  # shown above.
  # config.vm.synced_folder ".", "/vagrant", disabled: true

  # Provider-specific configuration so you can fine-tune various
  # backing providers for Vagrant. These expose provider-specific options.
  # Example for VirtualBox:
  #
  # config.vm.provider "virtualbox" do |vb|
  #   # Display the VirtualBox GUI when booting the machine
  #   vb.gui = true
  #
  #   # Customize the amount of memory on the VM:
  #   vb.memory = "2048"
  # end
  #
  # View the documentation for the provider you are using for more
  # information on available options.

  # Enable provisioning with a shell script. Additional provisioners such as
  # Ansible, Chef, Docker, Puppet and Salt are also available. Please see the
  # documentation for more information about their specific syntax and use.
  # config.vm.provision "shell", inline: <<-SHELL
  #   apt-get update
  #   apt-get install -y apache2
  # SHELL


  ipv6_prefix = 'fd00'
  ipv6_node_prefix = "#{ipv6_prefix}:10::"
  ipv6_cluster_network = "#{ipv6_prefix}:42::/56"
  ipv6_service_network = "#{ipv6_prefix}:43::/112"
  ipv4_node_prefix = "10.10.0."
  ipv4_node_offset = 100
  ipv4_cluster_network = "10.42.0.0/16"
  ipv4_service_network = "10.43.0.0/16"

  %w[libvirt virtualbox vmware_desktop].each do |p|
    config.vm.provider p do |v|
      v.cpus = 2
      v.memory = 1024 * 2
    end
  end

  packages = <<-SHELL
sed -i 's,https://mirrors.edge.kernel.org/ubuntu/,http://sg.archive.ubuntu.com/ubuntu/,' /etc/apt/sources.list
export DEBIAN_FRONTEND=noninteractive
#apt-get update
#apt-get upgrade -y
#apt-get install -y nfs-common
SHELL

  net_write = <<-SHELL
# Undo Vagrant setting
sed -i 's/net.ipv6.conf.all.disable_ipv6 = 1//' /etc/sysctl.conf
sysctl net.ipv6.conf.all.disable_ipv6=0
# Set up the second network interface
cat <<EOF > /etc/netplan/20-private.yaml
---
network:
  version: 2
  renderer: networkd
  ethernets:
    eth1:
      addresses:
        - $1
        - $2
      routes:
        - to: default
          via: "#{ipv6_node_prefix}0"
EOF
netplan apply
  SHELL

  ipv4_node_1 = "#{ipv4_node_prefix}#{ipv4_node_offset+1}"

  (1..3).each do |i|
    config.vm.define "node-#{i}" do |node|
      node.vm.hostname = "node-#{i}"

      ipv4 = "#{ipv4_node_prefix}#{ipv4_node_offset+i}/24"
      ipv6 = "#{ipv6_node_prefix}#{i.to_s(16)}/64"
      node.vm.network "private_network", ip: ipv4, auto_config: false

      # Install packages
      node.vm.provision "shell", inline: packages
      # Configure networking
      node.vm.provision "shell", inline: net_write, args: [ipv4, ipv6]
      # Install k3s
      node.vm.provision :k3s, run: "once" do |k3s|
        # This section runs the installation script with a configuration file,
        # environmental variables and a specific version.
        k3s.args = %w[server]
        k3s.env = %w[
          INSTALL_K3S_VERSION=v1.28.7+k3s1
          K3S_KUBECONFIG_MODE=0644
        ]
        k3s.config_mode = '0644'
        k3s_config = {
          :token => 'vagrant-k3s',

          :'flannel-iface' => 'eth1',

          :'flannel-backend' => 'host-gw',
          :'flannel-ipv6-masq' => 'true',
          :'cluster-cidr' => "#{ipv4_cluster_network},#{ipv6_cluster_network}",
          :'service-cidr' => "#{ipv4_service_network},#{ipv6_service_network}",
          :disable => %w[local-storage],
        }
        if i == 1
          k3s.config = k3s_config.merge(:'cluster-init' => 'true')
        else
          k3s.config = k3s_config.merge(:server => "https://#{ipv4_node_1}:6443")
          k3s.skip_start = true  # We'll manually start other servers later
        end
      end
      # Enable bash completion
      node.vm.provision "shell", inline: "kubectl completion bash > /etc/bash_completion.d/kubectl"
      if i == 1
        # Apply default manifest
        node.vm.provision "file", source: "manifests", destination: "$HOME/manifests"
        node.vm.provision "shell", inline: "sleep 15; kubectl apply -Rf $HOME/manifests/", privileged: false
      else
        # Wait for boot
        node.vm.provision "shell", inline: "sleep #{5*i}; while ! curl -o /dev/null --insecure https://#{ipv4_node_1}:6443; do sleep 2; done"
        # Start k3s
        node.vm.provision "shell", inline: "systemctl enable --now k3s"
      end
    end
  end


end