Another view showing the side by side setup better. Unfortunately I can only run one miner at a time at this location because I only have one ethernet connection here, so when it's hot I run the S5 but slide it back so that it exhausts out the wall vent. R-Pi controller draws 2.6 watts, wish they made an inexpensive meter for the 240v line, all I could find were in-line devices that cost on the order of $100. I am moving next month and will have a new laundry room to turn into a home mining area.
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Just get a small 4 port ethernet hub there and you can have both of them running if you have enough power.
The ethernet feed to that location is one that is already coming off a 6 port hub, and I don't think you can hub off another hub so no dice. Not to worry, next laundry room mine will have more connectivity.
If by "hub" you do mean switch, then yes, you can have a switch behind another switch.
Hubs are not common equipment these days, but you could do so with a hub as well, but a true hub spams the packet to every port, so much worse. A switch is managed or unmanaged but either way it will not spam every port with each packet once it is told or learns where the packet needs to be sent.
I've never done it, but I believe you can go 6 deep, not that I ever would. I am two deep at this time for one miner in one room just because I haven't pulled it out yet.