On Tue, 2021-03-02 at 08:33 +1100, Cameron Simpson wrote:
Aye. FWIW, in a former life the place I worked at made all our crossover cables yellow so that we knew what we were looking at.
I'd always understood that gigabit didn't need crossover cables, though just read that it's in the spec that gigabit can handle peer to peer without a crossover cable, devices don't actually have to incorporate that features into themselves. Argh! Back to square one.
Autocrossover was possible on 10/100 megabit ethernet devices, too, but much more rarely implemented.
The old 10/100 ethernet crossover cable just crosses over two pairs in the cable, and ignores the other two pairs (completely ignores them, they're generally not used at all, and not crossed over). Cheap ethernet cables bundled with some routers didn't even wire up the spare 4 pins.
Gigabit ethernet cable crosses over all four pairs.
So, label your cables (half-crossed, fully-crossed, 2-pairs crossed, 4- pairs crossed, whatever label makes the most sense to you).
Quite a few of us only connect computers together through switches or routers, so don't use crossover cables. But some of us also have connect a switch to a switch, when doing inter-room networking. I wonder how many routers or switches stuff-up auto crossover?