If you want to use the CS18AI only as controller in a direct ethernet connection, you don't need an AVB switch. If you want to use its I/O (microphone & line inputs, headphones) and if you want remote control (iPad), there is no way around an AVB switch. There is nothing else to buy than this expensive MOTU switch. Feel invited to read more about CS and RML in the forums. If you have a question, ask the experts who work with the equipment... ;-)