Alice and Bob try to talks each other

Vagrantfile

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

# Vagrantfile API/syntax version. Don't touch unless you know what you're doing!
VAGRANTFILE_API_VERSION = "2"

Vagrant.configure(VAGRANTFILE_API_VERSION) do |main_config|
  main_config.vm.define :alice do |config|
    # All Vagrant configuration is done here. The most common configuration
    # options are documented and commented below. For a complete reference,
    # please see the online documentation at vagrantup.com.

    # Every Vagrant virtual environment requires a box to build off of.
    config.vm.box = "debian-wheezy64-bearstech"
    config.vm.box_url = "http://download.bearstech.com/vagrant-debian-wheezy64-bearstech.box"

    # Create a private network, which allows host-only access to the machine
    # using a specific IP.
    config.vm.network :private_network, ip: "192.168.33.53"
    #config.vm.provision :shell, inline: "sudo /sbin/ifdown eth1 && sudo /sbin/ifup eth1"

    # 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|
    #   # Don't boot with headless mode
    #   vb.gui = true
    #
    #   # Use VBoxManage to customize the VM. For example to change memory:
    #   vb.customize ["modifyvm", :id, "--memory", "1024"]
    # end

  end
  main_config.vm.define :bob do |config|
    # All Vagrant configuration is done here. The most common configuration
    # options are documented and commented below. For a complete reference,
    # please see the online documentation at vagrantup.com.

    # Every Vagrant virtual environment requires a box to build off of.
    config.vm.box = "debian-wheezy64-bearstech"
    config.vm.box_url = "http://download.bearstech.com/vagrant-debian-wheezy64-bearstech.box"

    # Create a private network, which allows host-only access to the machine
    # using a specific IP.
    config.vm.network :private_network, ip: "192.168.33.52"
    #config.vm.provision :shell, inline: "sudo /sbin/ifdown eth1 && sudo /sbin/ifup eth1"

    # 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|
    #   # Don't boot with headless mode
    #   vb.gui = true
    #
    #   # Use VBoxManage to customize the VM. For example to change memory:
    #   vb.customize ["modifyvm", :id, "--memory", "1024"]
    # end

  end
end

on a terminal :
vagrant ssh bob
on another terminal:
vagrant ssh alice