The best you can do is search on IDnet http://www.ni.com/devzone/idnet/ and if the device driver ( a bunch of vi's and examples) is available use it as an interface.
Ethernet is a communication channel just as rs232 and gpib, only a bit cheaper and faster than those.
I'd also like to add that you should go into MAX and in the configuration pane, right click on Devices and Interfaces, and select Create New>VISA TCP/IP Resource. Once that has been configured, then you should be able to use a driver or your own VISA functions.
Since your question has nothing to do with communicating to an R&S instrument over Etherenet, please post your question in a new thread. Provide additional details like LabVIEW version, error codes that you get, etc.