Abstract: The present invention provides for automatic addressing of devices on a rack controller bus. As each tracing interface module in a rack is powered up, the device identifies its electronic serial number (ESN) to the rack controller via the rack controller bus. The ESN includes information identifying the type of module, and the number of ports on the module to the rack controller. The rack controller maps the module's ESN to a unique address, which it sends back to the module. In subsequent communications, the module uses this address to identify itself to the rack controller, and the rack controller uses this address to track the location of patch connections to the module. If a module is replaced, the rack controller tracks the replacement using the same address assigned to the original module.