An end system device for a network system, wherein the end system device comprises: - a first port for connection with the network system; - a second port for connection with the network system; - a local interface; - a switching device; wherein the switching device is designed for switching into a first or a second mode; and wherein: - in the first mode, the switching device is set up to relay data received at the first and second port only to the local interface, and relay data received at the local interface to the first port and the second port wherein, in the first mode, the first port and the second port are used for connection with two independent networks of a network system and, in the first mode, the data of the local interface are output identically on both networks of the network system, and wherein, in the first mode, packets or data are not relayed between the first port and second port; and - in the second mode, the switching device is set up to relay data received at the first port to the second port or to the local interface, relay data received at the second port to the first port or to the local interface, and relay data received at the local interface to the first port and the second port, and wherein, in the second mode, the switching device is designed to relay data received at the first port to the local interface if the data or data packet are intended for the end system device and, otherwise, to relay the data received at the first port to the second port if the data or data packet are not intended for the end system device, - the local interface is used for connection and local communication with local components of the end system device. - a first port for connection with the network system; - a second port for connection with the network system; - a local interface; - a switching device; - in the first mode, the switching device is set up to relay data received at the first and second port only to the local interface, and relay data received at the local interface to the first port and the second port wherein, in the first mode, the first port and the second port are used for connection with two independent networks of a network system and, in the first mode, the data of the local interface are output identically on both networks of the network system, and wherein, in the first mode, packets or data are not relayed between the first port and second port; and - in the second mode, the switching device is set up to relay data received at the first port to the second port or to the local interface, relay data received at the second port to the first port or to the local interface, and relay data received at the local interface to the first port and the second port, and wherein, in the second mode, the switching device is designed to relay data received at the first port to the local interface if the data or data packet are intended for the end system device and, otherwise, to relay the data received at the first port to the second port if the data or data packet are not intended for the end system device, - the local interface is used for connection and local communication with local components of the end system device.