_______             ________
                         |       |    WAN    |        |
             ------------|  R1   |-----------|   R2   |
             |           |_______|           |________|
             |                                   |
          ---------                           --------  
        --| CAT 1 |--                        | CAT 2  |---------
       |  ---------  |                        --------         |
       |             |                           |             |
      -------      -------                     ------        -------
       vlan1        vlan2                       vlan1         vlan2