Just had a real life experience of a bad ethernet cable hurting my network. My Linux server (or rather, the 4 port switch it is connected to) sometimes gets gigabit ethernet, sometimes 100 MBit. I couldn’t figure out why, but today I was frustrated it was stuck at 100 MBit so I found the actual cable in the patch panel and replaced it. Boom, gigabit ethernet.
I’ve got fairly elaborate-but-janky ethernet wiring in my house. Some 20 cables in the walls punched down into a cheap Leviton patch panel. Then short patch cables from the panel to the switch. In retrospect the patch panel is probably overkill; I’m never gonna repatch it. And it adds two more connectors, some circuit board traces, and a patch cable to every cable run. Still it mostly seems to do gigabit ethernet fine, just wish we hadn’t used cheap patch cables. They don’t have any rating printed on the jacket at all, just some numbers that boil down to basic Underwriter Lab type building codes. They’re flat, and in my experience flat cables tend to be crap.
Time to replace all the patch cables. Happily I found some gay pride Cat6