I'm using Lenovo G480 and I have problem with LAN cable not detected if it is connected to Router. However if it is directly connected to modem everything works fine. I did so many remedies including uninstall/install LAN driver, remove the battery for 30 minutes and more but no luck the problem still persists.
Updated If the LAN cable or internet cable is directly connected to a router the light that shows if you are connected to internet is not blinking (totally dead. No sign of light). Other machines or work stations are connected to the same router but they are working fine. They have internet connection. Both routers in our office and at home with the different models are not detected by my laptop. However if I unplug the cable from router and connect it directly to Modem my laptop internet connection will become alive.