I may be wrong for some products but if you want to use IP control and the product and driver support that, you do not need to use up one of the RS232 ports on the XP8. If you are going to use a 2way driver and set it up for RS232 control then you would use a port.
You of course have to set up the device being controlled, and then input the IP address into the RTI driver so it knows where to send the commands.