12. Ethernet Cables

As of the end of the last page, you’ve cut each plastic part one time. Assuming you’ve been successful with each step, you should now cut and assemble the remaining cards before making your Ethernet cables. If you have not done this already, do so now.

For the Ethernet cables, I recommend the following guidelines:

  • You will need to select either the T-568A or T-568B standard for your Ethernet cables and stick with it through this project. The EF4124 doesn’t support autonegotiation, so your cable just won’t work if you accidentally make a crossover cable by mistake. So be consistent about which standard you choose.
  • Use the top switch first until you’ve plugged 20 cables into it, then use the bottom switch.
  • Populate the cables in the switches from right to left.
  • Alternate between the top and bottom ports in each column so you don’t cover any ports before they’re used.
  • Plug the Pis in from right to left.
  • Exclusively use the front-side (your right side, if you’re facing the left side of the case) wire management for Ethernet cables.
  • Make sure you’re always using space in the wire management efficiently. If you don’t, you simply won’t have enough space for all the cables. Try installing the front panel frequently to check how much space you have left for more wires. If you’re running out of space, go to the effort to repack them before moving on.

Step 1. Connect Switches to Router

Connect a temporary cable from the leftmost side of each switch to a port on the router. This will allow for testing the cables as you make them.

Step 2. Connect the 40 Pis

For each row of Pis:

  1. Tip one end of a cable and plug it into the switch. Route it through the cable management (as you intend to when it’s routed properly) up to rightmost Pi in this row. Cut this cable so that it barely reaches the Ethernet port for the next Pi from the rightmost one.
  2. Remove the cable you just made from the case.
  3. Cut 3 more cables from the same color. Cut each one successively about 3.5 inches longer than the last.
  4. Tip the other 3 cables on one end.
  5. Color code one end with zip ties. I liked to use the following code: red, green, blue, white (from shortest to longest). What you need to do is attach a zip tie to each cable just behind the tip, then trim the excess from the tie.
  6. Plug the cables into the switch. I recommend using a consistent pattern to plug them in, so you have an idea of which is which simply based on which port it’s connected to.
  7. Route the cables up to the Pis. Try to route them as tightly as possible, but not so tightly that you crack a wire management clip in the process. Kinking the cables as you go will help to make them lay the way they should.
  8. When all four cables are routed up to the level of the Pis you want to connect, push them tightly into the cable management comb slot for that row in a 2×2 pattern and use a zip tie to secure them this way. This practically locks them in place and will help to prevent them from shifting out of the wire management while you’re tipping their other ends.
    Wire Management Detail
  9. Cut all four cables to length. When I was cutting mine, I used the second zip tie hole from the port as my cutting guide, as shown in the image below. When you’re ready to cut the longest cable to length, just leave about the same amount of excess as you did for the other ports in the row.
    Where to Cut Detail
  10. Strip the jacket from the end of each cable. When you’re stripping the jacket, you will need to cut the bare minimum. To do this, you’ll want the end of the cable to be roughly flush with the appropriate part of the crimper when you’re using it to cut through the jacket. This will give you just enough exposed wire to install the tip.
  11. Arrange your wires according to your chosen T-568 standard and trim them just enough to make them even with each other. Test fit them with the tip and look to make sure they reach past the second pin on the contact before crimping them. If a few of them don’t reach, you may need to even them up a second time or strip a little more off the jacket.
  12. Crimp the tip to the cable. Make sure you crimp it tightly.
  13. Color code your cables with zip ties as you finish each tip.
  14. Test your cables by turning on your router and connecting the end of your new cable that you just tipped to your desktop computer through another cable and an inline coupler. If your new cable works, you should be able to load the router’s status/configuration page.
  15. If your cables tested good, connect your row of Pis and carry on with the next row. If necessary, bend the clips of your tips outward slightly so that the tip locks in place when it’s plugged in.

Do the above steps until all 40 Pis are wired up.

Step 3. Connect Switches to Router

Make 2 very small cables to connect your switches to your router. I did not bother routing these two cables through the wire management, but feel free to do so if you have any room left in yours. I chose red as the cable color for my upper switch and green as the cable color for my lower switch. You would not need to follow this color code if you like something else better.

Step 4. Wire Ethernet Jacks

Wire up your Ethernet jacks. I recommend just leaving a little extra length on them and waiting to tip them after they’re attached. That way you’ll more easily get them the right length. After your cables are tipped, you’re sure they’re long enough, and you’ve tested them, bundle them and glue your keystones into the mounts. Or, leave them unglued if you feel they’re tight enough as-is.

Step 5. Bundle Your Cables

Use large zip ties to bundle the cables in your wire management. Take care not to wrap up any of the card-retaining clips in the process. I found that bundling the cables tightly in this manner was necessary to allow enough clearance for the front panel.

When you’re done, your Ethernet cables should look something like the following images.

Cluster - Left Side Angled Cluster - Front Side Detail Cluster - Front Side

11. Hard Drive Array 12. Ethernet Cables 13. Power Cables

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