I have a usb-lan DAVICOM Semiconductor, Inc. that work good
when I connect it with a pc it say that cable unpluged but cable is ok and pc connected to internet well.
sorry because of my english(i'm from Iran)
Go to your network connections. You likely have multiple network connections setup. You can disable the one that says it's unplugged, and it will get rid of that notification. Your lan connection should still be enabled, and you should still be able to access the internet.