Hi,
First of all, make sure you have the firmware version that is the latest available one.
After that, the monitoring port - in your case (LAN1), should be the one your computer is connected to (analysis port). And switch0 should be the port that is connected to other devices that you want to monitor (monitored port).
Also, check if your RUT955 has TCP dump enabled and had time to gather the packets.
EB.