The information in the header portion of a data packet, which header includes the old module and channel numbers, is used to access locations in a random access memory which contain new module and channel numbers or words that identify the packet routing. To convert the "virtual" address defined by the old module and channel numbers to a physical address, the module number accesses a memory word which is combined with the channel number to produce a single physical address number. When the information stored in the memory is to be changed, the header has special module and channel numbers and the following data includes a "write" command word, address data and information data. The special header words access a memory word which enables the writing of the information data into memory locations selected by the address data. A "read" command word in the packet inserts the word accessed by the address data into the packet.