category 5 utp cable is required for fast ethernet operation. the maximum cable run between the dfe 550tx and the supporting hub or switch is 100m. the cable must be straight-through (not a crossover cable), with an rj-45 plug at each end. make the network connection by plugging one end of the cable into the rj-45 jack of the dfe-550tx, and the other end into a normal (non-uplink) port on the supporting device.