A method and an apparatus for selectively accessing and independently sizing connection identification tables (70) within a network switch. Upon receipt of a data unit, such as an ATM cell, at an input port of an Input/Output module, a plurality of selection bits are inserted into the cell header which are used to select one of a plurality of connection identifiers. The VPI/VCI addresses are mapped into a connection identifier and the connection identifier is also inserted within the respective cell header. The connection identifier (CID) may comprise a unicast, a multicast or a redundant unicast CID, which are either stored in separate tables at call setup and the tables are independently selectable via use of selection bits stored within the cell header. Alternatively, the selection bits are employed to specify a register which points to the first address for the respective type of identifiers. Thus, identifiers of a particular connection type are accessible via an address of a base (60, 62 or 64) plus an offset address.