a fluke tester is used to check connectivity, the network cable pinouts, cable length and cross interference. Attach the tester to one side, and either leave it connect or attach a terminator to the other and test it. It will tell you if the cable is okay, the length of the cable (cables if more than one) and any sort of signal loss. If it comes up okay, then you can rule out a bad cable, and if through a switch and comes up okay then more than likely the switch is okay, too.
If you argue with an idiot he will drag you down to his level and beat you with experience.
I am not a fast writer.
I am not a slow writer.
I am a half-fast writer.