James Hess <mysidia@gmail.com> wrote:

Auto MDI/MDI-X is an optional feature in the 1000BaseT standard.

Can someone please explain how can the whole MDI vs. MDI-X distinction be meaningful at all for 1000BaseT? I thought they run 250 Mbps on each of the 4 pairs in both directions using some form of echo-cancelling hybrid techniques. If one no longer has separate Rx and Tx pins, how is it meaningful to talk about MDI or MDI-X? I thought that for 1000BaseT a straight-through cable was always the "native" cable choice for connecting any two ports, be they switch ports or station ports - is that not true? It also seems to me that a crossover cable should never make sense for 1000BaseT, but from what I understand such cables do work because the PHYs are generally smart enough to detect "hey, I'm seeing signal on pair B that ought to be on pair C" and auto-correct. MS