(d)                      (m)
  -------                    ____
  |     |     <==========>  |____| {61.54.10.20}
  |     |
  -------     <=======
  {192.168.0.1}       |      (a)
                      |     |    |
                      |     ------
                      |===  |    |
                            ------
                        {192.168.0.2}


   (l)
   --
    \\
     \\
      =======
      {192.168.0.3}