When using LST Server, it's simple...Just select your NIC under 'Listening NIC + Port' and click on 'Reset Server'. For LAN Speed Test, however, Windows does not give us an easy way to manually choose which NIC to use as a client. Windows tries to figure out which NIC is performing the best and then chooses that one to route IP traffic. With that being said, I know of two different ways we can get around that...The first option (the easiest, but probably least desirable), is to first disable the NIC that you don't want to use, and then run LAN Speed Test. The second option, is to go into your LAN NIC settings, Select 'Internet Protocol (TCP/IP)', select properties, select advanced, uncheck automatic metric, and adjust accordingly as suggested in this article...http://support.microsoft.com/kb/299540.