Control unit and method for operating an industrial automation system communication network comprising a plurality of communication devices

A control unit and method for operating an industrial automation system communication network that includes a plurality of communication devices, wherein a plurality of control units redundant with respect to each other controls functions of a plurality of associated communication devices, where the communication devices transmit communication-specific input variables to all associated redundant control units, output variables (produced by the control units redundant with respect to each other are checked for deviations from each other, and where if there are deviations, then a switchover is made to reserve control units or control units having output variables that deviate with respect to a majority of control units redundant to each other are deactivated.