This Dell Inspiron 580s Desktop has stopped connecting by ethernet (it has no wireless). It could be hardware but how can I troubleshoot it without a network connection? I have tried many ethernet connections and 2 different routers. I wouldn't mind buying and installing a new network card but not having luck seeing how to do that or even if it could be a software issue. I am running Xubuntu 16.04 64bit on it. Thank you,