[charlieo88]

Something that always bothers me about these Pi clusters is the Ethernet cable lengths. Isn't there a minimum length?

[dsr_]

10cm for 1000BASE-CX, nothing prior specified a minimum length.

[rwmj]

That's really interesting - do you know why there is a minimum?

Maximum lengths are easy to understand because of voltage drops, interference and impedance over long distances. And of course in the old CSMA/CD days multiple senders couldn't be separated by too large a distance.

[MisterTea]

signal reflection most likely. https://en.wikipedia.org/wiki/Signal_reflection