Vagrantfile to create three FreeBSD 12.0 VMs in a private subnet 192.168.10.0/24.

Vagrantfile

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

Vagrant.configure("2") do |config|
  config.vm.box = "bento/freebsd-12.0"

  config.vm.define :r1 do |node|
    node.vm.hostname = "r1"
    node.vm.network "private_network", ip: "192.168.10.1", virtualbox__intnet: "wgnet"
    node.vm.provider "virtualbox" do |vb|
      vb.name = "r1"
      vb.memory = "512"
      vb.cpus = 1
      vb.gui = true
    end
  end

  config.vm.define :r2 do |node|
    node.vm.hostname = "r2"
    node.vm.network "private_network", ip: "192.168.10.2", virtualbox__intnet: "wgnet"
    node.vm.provider "virtualbox" do |vb|
      vb.name = "r2"
      vb.memory = "512"
      vb.cpus = 1
      vb.gui = true
    end
  end

  config.vm.define :r3 do |node|
    node.vm.hostname = "r3"
    node.vm.network "private_network", ip: "192.168.10.3", virtualbox__intnet: "wgnet"
    node.vm.provider "virtualbox" do |vb|
      vb.name = "r3"
      vb.memory = "512"
      vb.cpus = 1
      vb.gui = true
    end
  end
end