The Red RD LED means that the sensed network I/O and the configuration does not match. You must have all the I/O-bus network I/O cards mapped correctly and installed for the remote bus to run. Before the CPU starts the remote bus it will compare the I/O map to what is physically connected. If there is a difference the I/O will be disabled and the Red RD LED illuminated on all of the I/O-bus modules. This will also occur if any of the cables are broken, disconnected, or if a base fails. This also means that you cannot preconfigure I/O in the I/O map for future expansion or have any I/O bases on the bus that are not mapped.