A switch unit for an Ethernet network having a switch and a microprocessor, the switch including at least three ports, which are connected to inputs and outputs of the switch unit, a signal detector and generator for detecting and initiating a bus activity being arranged in each case between the ports and the inputs and outputs of the switch unit. For each input and output an allocation rule to the other inputs and outputs of the switch unit is stored in a memory, the switch unit being designed such that when a bus activity is detected at a signal detector and generator, the assigned inputs and outputs of this input and output are read out from the memory and the associated signal detectors and generators are woken up so that they generate a bus activity at their inputs and outputs.