~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
            /         internet           /
           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 
             |                        |
             |                        |
          +--+--+                     |
          |  R2 |                     |
          +--+--+                     |
             |15                      |
             |                        |
       ------+--                   +--+--+
 201.y.y.0   |                     | R1  |
             |                     +--+--+ 
          +--+--+                     |15
          |CSS  |                     | 
          +--+--+                     | 
             |                        |
            -+----------+-------------+---------
                        |                  200.x.x.0
                        |1
                    +---+---+
                    |       |default gateway is CSS
                    |  FW   |
                    |       |
                    +---+---+
                        |
                        |
                 ---+---+------+-- 10.111.110.0
                    |93        |94
                 +--+--+    +--+--+
                 | S1  |    | S2  |
                 |     |    |     |
                 +-----+    +-----+