Hello - When I try to connect a Dell Inspiron 1525 to my modem or router with a LAN cable, I cannot. The small lights on the LAN cable socket are: upper right is dark orange, and upper left is blinking yellow - very evenly, about 10 times, then missed a couple; then repeating. On another laptop, which works, the upper right light on the cable connector is green, and upper left is blinking yellow- irregularly, like data is being moved. I suspect there is a problem with the Dell adapter, but diagnostics seem to indicate "working correctly".
When I try wireless, I cannot connect to my router, but can connect to other wireless networks.
I suspect 2 problems - one with the router (the wireless part, since a cable from the modem to the router then to another computer allows internet connection); and the second with the Dell laptop, with the steady orange light on.
I don't know if you are looking at your laptop upside down or not, but look at the back of my D620 laptop with a working Ethernet + internect connection, the upper Left LED is solid orange and the upper Right LED is blinking yellow.
my Dells:Optiplex 3020 - Windows 7 Pro 64-bitPrecision M6300 - Windows 10 Pro 64-bitPrecision M6300 - Linux Mint 17.3 Rosa / Ubuntu 12.04.5 dual-bootLatitude D620 - XP Pro SP3