R6250 Ethernet connection drops constantly

I have tried to connect my desktop to the R6250 router and the ethernet connection continuously drops and connects about every three to five seconds.  The wireless works fine for the desktop and all other devices.  When I connect my desktop directly to the modem, there is no dropped connection.  Also, when I connect a different laptop to the R6250 router with the ethernet cable, there is no issue of a dropped connection.

Any help would be greatly appreciated!

Thanks

Dan