📘 02-02: Racks, Patch Panels & Terminations¶
📌 Equipment Racks¶
- Standard rack width is 19 inches; height is measured in rack units (U), where 1U = 1.75 inches.
- A common full rack is 42U.
- Devices are described by height: a "1U switch," "2U server," etc.
- A rack diagram (rack elevation) documents which device sits at which U position.
📌 Patch Panels¶
A patch panel terminates permanent horizontal cable runs. Short patch cords then connect panel ports to switch ports.
- Keeps cabling organized and easy to re-patch.
- Horizontal runs are punched down into the back of the panel with a punch-down tool.
📌 Termination Standards: T568A vs. T568B¶
Two pin/pair color schemes define how the 8 conductors map to the RJ-45 pins:
| Cable type | Ends | Use |
|---|---|---|
| Straight-through | Same standard both ends (B–B) | Unlike devices: PC ↔ switch |
| Crossover | T568A one end, T568B the other | Like devices: switch ↔ switch (legacy) |
| Rollover | Reversed | Console cable to router/switch |
- Be consistent — use the same standard on both ends unless intentionally making a crossover.
- Auto-MDIX on modern switches auto-detects cable type, making crossover cables mostly unnecessary.
🧰 Tools¶
| Tool | Purpose |
|---|---|
| Punch-down tool | Seat wires into 110/66 blocks and patch panels |
| Crimper | Attach RJ-45 plugs to patch cables |
| Cable tester | Verify wiremap (opens/shorts/miswires) |
| Toner probe | Trace/identify a specific cable in a bundle |
Tip
Key idea — Horizontal runs are punched down into patch panels; patch cords connect them to switches. Use T568B consistently (or A/B for a crossover), and remember 1U = 1.75 in.
See also: Structured Cabling, Cable Issues, Tools & PoE
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