Modular industrial automation device and method for configuring a modular industrial automation device, wherein in order to configure the modular industrial automation device which includes a central unit and at least one communication module which each comprise a router module and a routing configuration unit, the routing configuration units transmit routing information stored in their routing table to routing configuration units of other router modules, and the routing configuration units update their respective routing table based on routing information which is received from routing configuration units of other router modules and relates to routes to IPv4 subnetworks assigned to other router modules, a default gateway and a connection between the associated router module and a backplane bus system.