A network distributor comprises a plurality of input/output ports, a processor unit, and a memory unit. The input/output ports are configured to connect network subscribers via a data line network, where the network subscribers comprise protocol subscribers configured to process telegrams configured as protocol telegrams. The processor unit is configured to receive telegrams via one input/output port and to output telegrams via another input/output port, which is stored in a routing table in the memory unit. The processor unit is further configured to determine whether a telegram is a protocol telegram received via an input/output port for which it is preset that no protocol subscriber is connected, and to discard the telegram if so. Checking and discarding of telegrams can be subject to a precondition, where fulfillment of the precondition leads to an exception from discarding the telegram.