Initial configuration has to happen using the controller’s serial port, so you'll need a cable like the one described here to set it up. Required connections for a Baytech RPC-3 RJ45 to DB9 NullModem? serial cable:
|RJ45 pin||DB9 pin||Role|
|4||2||(RPC-3 TX → PC RX)|
|5||3||(RPC-3 RX → PC TX)|
|3||8||(RPC-3 RTS → PC CTS)|
|1||6||(RPC-3 DTR → PC DSR)|
|2||5||(GND → GND)|
|8||1||(RPC-3 carrier detect → carrier present)|
Pins 6 and 7 on the RJ45 side can remain disconnected, along with pins 4, 7 and 9 on the DB9 side.
Tested and working on an RPC-3 using a USB-to-serial adapter.