D-Link router                             My linux box                          3Com router
DSL shop -> [ISP/192.168.0.0] -> [eth1: 192.168.0.101 / br0 = /eth0: 192.168.200.101]  <- [192.168.200.0/ISP] <- DSL
                                                     /        \tap0: 192.168.200.(201-254) <--- OpenVPN