H1            PIX       R1     R2

H1 cannot see R2
R2 cannot ping PIX other int
R2 can reach PIX one int   

H1:192.168.2.84/24
      *192.168.2.1
PIX: 192.168.2.1/24
        192.168.0.1/24
      *Real IP in the real world
R1: 192.168.0.20/24
       192.168.4.1/24
       *192.168.0.1
R2: 10.0.104.1/24
       * s0/0.1 ==> R1