White macbook early 2008. Ethernet connection okay. However no internet. Safari en appelstroop cannot find servers. With WIFI everything works well.

I have a white macbook early 2008. When I connect it with my Airport Extreme with an ethernet cable, the ethernet connection is established accorcing to system preferences/network/ethernet, incl IP adres. However no internet is available. With WIFI there is no such problem. Used three different sabbelen to no avail. Connected my 2008 Imac in the same way and internet runs okay. Anybody with a solution?