Try another port on the router. Hardware does die sooner or later.
I have a computer that is connected to the internet through a SMC 7004VBRM Router. On the router, I have 4 clients setup, two computers that connect with cables, one computer that uses an wireless adapter, and a laptop. All of them have been working flawlessly for a very long time, but yesterday- one of the computers internet stops all of a sudden.
I tried connecting the computer directly to the internet (without going through the router), and it works again. but for some reason, the computer just doesn't work when i try to connect using the router.
Any help?

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