GCNrd
From Wiki - GameHacking.org
GCNrd is remote debugger tool for the Gamecube that allows players to create unofficial Action Replay codes. It is a PC program that interacts with the Gamecube through the use of the Gamecubes broadband adapter. It must be used in conjunction with either a Network Interface card + Cat5 crossover cable or a port on a router or network switch + 2 Cat5 "patch" cables. For information on how to setup and use the GCNrd click this link.