If your LAN ports doesn’t work …

Don’t try to reinstall the OS / driver immediately, check to see if it works with different switch first, some older LAN ports can’t work with specific (maybe newer) switches, even if you try to reinstall the OS / driver.


Tips for checking long UTP cable (or any other cables)

Just short circuit all wires on the other end, and check the other one by using a multitester.

Also, instead of multitester, you could just use a power source e.g. a battery and a small light bulb.
The end product would look like this :