The switch fabric of the ATM switch, i.e., the ATM switch backplane bus, switches a cell based on routing information provided by the source LAN or ATM module to an output port on a destination LAN or ATM module of the switching hub. In the described system, the ATM switch is preconfigured to provide a fully connected topology between ports of all modules. In one embodiment, ATM cells transmitted across the ATM switch fabric between a source LAN or ATM module and a destination LAN module, e.g., Token Ring, FDDI or Ethernet, is accomplished by way of a routing tag prepended on the ATM cells. The routing tag provides both unicast and multicast group destination information such that the ATM cells are routed to the appropriate port on a given destination module without the need to establish a virtual circuit between the source module and the destination module using VPI/VCIs.