I only tried with Twincat as an Ethernet/IP Scanner and robot as an adapter.
In Twincat : You do as you have a real robot. In the settings of the ethernet adapter you select your second ethernet adapter (the USB one for me).
In the master settings you can set any ip address in the same subnetwork
In the slave settings, you enter the settings of your first ethernet adapteur.
In Roboguide : In the TCP/Ip settings you enter the IP address of your first ethernet adapteur
Then you can activate the configuration with twincat and run it. If all is Ok, the status of your connection1 in roboguide should be "RUNNING" in the ethernet/IP Menu