define firewall::virtual::ssh(
  $destination,
  $port_orig      = '22',
  $port_dest      = '',
  $zone           = 'vm'
  $implementation = lookup('firewall::implementation', undef, undef, 'shorewall'),
) {
  class { "firewall::implementations::${implementation}::virtual::ssh":
    destination => $destination,
    port_orig   => $port_orig,
    port_dest   => $port_dest,
    zone        => $zone,
  }
}