Ubuntu wired coection not working when Windows 10 works.

Whilst doing some work on the wiring of my home wired network, I have developed a problem where Ubuntu 15.10 is unable to coect via etheet. There are - to me - a number of very puzzling features of this situation. Firstly, my Ubuntu 15.10 dual boots with Windows 10, and the Windows 10 etheet coection, sharing the same wiring and interface, does not have a problem. Secondly, I had a DVD with Ubuntu 15.10 and booted into a live version ruing from the DVD. Again this results in no Inteet coection via etheet. This evening I bought a beta version of 16.04 on DVD and again booted up using this disc, with the same result.

I have been watching the small neon lights on the etheet coection on the reverse of the computer as it boots up. These flash to begin with - indicating a coection. They continue to flash until the GRUB menu appears and for a short time thereafter, if I select Ubuntu 15.10. Then the lights stop flashing and when the boot sequence is complete, network manager tells me that a network cable is unplugged. Needless to say this is not the case. Selecting Windows 10 on the other hand results in a continuous flashing of the neons until the boot sequence is complete at which point the Inteet is available.

It is important to point out that I have been using Ubuntu 15.10 since it first came out, without any difficulty of this kind. Other devices on the wired network continue to work. My wireless network continues to work [I access these via my android phone and on the chromebook I am using for this post] This is a recent problem, possibly associated with me plugging and unplugging coections from the router in order to determine which cable was coected to which device on my network.

My coection is superfast broadband. My router is a netgear D6400 .