Dl 624 router

Just recently I am getting local connection unplugged messages and the ethernet connection thru the router goes down. At first I could restore by power-down and power-up, but now it just stays down(all lights on router indicate router is functioning) Has the router(or a port) died, and is there any way for a novice such as myself to perform dianotics on it? All connections thru the router are cabled. I gave up using it wireless two years ago.