My ethernet data speed slowly slows down until it doesn't work. How do I fix this.

Question

So as the title says, I plug my MacPro into hard wired ethernet and slowly but surely my data speeds drop to the point that I have to unplug the ethernet and go back to using wifi. Then if I restart the computer and plug it back in it'll work fine for a little and start to do the same thing. Is there anything I can do to fix this problem.
Thanks,
Rick

Answer 1

Please read this whole message before doing anything.
This procedure is a diagnostic test. It won’t solve your problem. Don’t be disappointed when you find that nothing has changed after you complete it.
The purpose of this exercise is to determine whether the problem is localized to your user account, or is system-wide. Enable guest logins and log in as Guest. For instructions, launch the System Preferences application, select “Help” from the menu bar, and enter “Set up a guest account” (without the quotes) in the search box.
While logged in as Guest, you won’t have access to any of your personal files or settings. Any application you run will behave as if you were running it for the first time. Don’t be alarmed by this; it’s normal. If you need any passwords or other personal data in order to complete the test, memorize, print, or write them down before you begin.
As Guest, launch the application(s) and test. Same problem(s)?
After testing, log out of the guest account and, in your own account, disable it if you wish. Any files you created in the guest account will be deleted automatically when you log out of it.