@dbSoft 

Hi, you are correct, not only the quality of the cable will influence the performance of EAP, but also the length of the cable does either.

  @dbSoft 

Within limits...ethernet is digital so it mostly either works or doesn't work, and of course there's a small zone in between where it sort of works :)

Mostly bad cable will do something like reduce your negotiated throughput to 100M instead of 1G.

Bad cable can also cause packet loss and thus retransmits and sense that things just aren't right, possibly some lag.

The fact that you are even asking the question means you already know what you need to do.