The RTC console is accessed via the DB-9 RS-232 serial connector (19200bps, 8-N-1) on the front of the controller marked "Maintenance". Be careful when using this interface, you can easily do pretty destructive things like rebooting the system or deleting critical files from the filesystem very easily from this interface.
As far as how the controller can have multiple IP addresses, it has an internal L2 switch that is configured via the System IP Configuration form, so check that for your duplicate IP. That also explains why the mystery MAC is only one off from the known RTC MAC address, as they're both in the controller itself.