late 2006 iMac has a working/not working ethernet

My late 2006 20inch iMac Ethernet, Built-in 10/100/1000BASE-T (Gigabit) sometimes works and sometimes not. I have tried different cables and using different outlets from the router. Sometimes it works when the iMac starts and then will stop working when there is a restart although it will start working again after a period of time such as half an hour.
As a work around would a USB type of connector work such as

D-Link® DUB-1312 USB 3.0 to Gigabit Ethernet Adapter

Item: 578401 Model: DUB-1312 shown here http://www.dlink.com/uk/en/support/product/dub-1312-usb-3-gigabit-ethernet-adapt er