RJ45 Pinout (T568A / T568B)
Straight-through: both ends same standard. Crossover: one A, one B. Most installs use B.
1
2
3
4
5
6
7
8
T568B — gold pins facing you, locking clip underneath. Pin 1 on the left.
T568B (most common)
1White / Orange
2Orange
3White / Green
4Blue
5White / Blue
6Green
7White / Brown
8Brown
T568A
1White / Green
2Green
3White / Orange
4Blue
5White / Blue
6Orange
7White / Brown
8Brown
Ethernet Categories
| Cat | Max Speed | Band | Max Run | Notes |
|---|---|---|---|---|
| Cat5e | 1 Gbps | 100 MHz | 100 m / 328 ft | Most common legacy copper |
| Cat6 | 1 Gbps (10G ≤55 m) | 250 MHz | 100 m; 10G to 55 m | Thicker, tighter twist |
| Cat6A | 10 Gbps | 500 MHz | 100 m / 328 ft | 10G full distance; often shielded |
| Cat7 | 10 Gbps | 600 MHz | 100 m / 328 ft | Shielded S/FTP; GG45/TERA ends |
| Cat8 | 25–40 Gbps | 2000 MHz | 30 m / 98 ft | Short data-center / switch-to-switch |
Fiber Strand Color Order (TIA-598)
Standard 12-fiber sequence. A 6-strand cable uses the top row; 12-strand uses both.
Strands 1–6
1Blue
2Orange
3Green
4Brown
5Slate
6White
Strands 7–12
7Red
8Black
9Yellow
10Violet
11Rose
12Aqua
More: strands 13–24same colors + black tracer
Strands 13–18
13Blue
14Orange
15Green
16Brown
17Slate
18White
Strands 19–24
19Red
20Black
21Yellow
22Violet
23Rose
24Aqua
Strands 13–24 repeat the 12 base colors, each marked with a black tracer (dashed ring/stripe). Beyond 24 the same colors repeat with different tracer marks, but you will rarely see past 12.
Fiber Connector Types
SC — square push-pull "stick and click," 2.5 mm ferrule. Patch panels, older datacom.
LC — small push-pull latch, 1.25 mm ferrule. Most common today (SFP/SFP+); usually a duplex TX/RX pair.
ST — round bayonet "stick and twist." Legacy multimode / campus.
FC — threaded screw-on, 2.5 mm ferrule. Older single-mode and test gear; rare in new installs.
MPO / MTP — multi-fiber ribbon (12/24+). Trunk cables, 40/100G breakouts.
Day to day you will mostly see LC (and LC duplex) on transceivers and MPO/MTP on trunks. ST and FC are legacy.
Fiber Polarity & Rolling
Every strand is one-way: Transmit (Tx) on one end must land on Receive (Rx) at the other. A duplex LC carries the pair.
No light / no link? Almost always Tx and Rx are reversed (Tx meets Tx). The fix is to roll the pair.
Rolling — on the LC duplex, twist the two connectors out of the clip, swap their positions (or flip the duplex boot), and re-seat. That flips Tx and Rx so the link comes up.
Roll one end only. Flipping both ends just puts you back where you started.
Most factory duplex cords are already crossed so Tx→Rx out of the box — you roll when a run is wired straight or the SFP shows no receive light. Quick check: a red VFL or the transceiver’s own light at the far end. Always clean the ferrule before seating, and keep both ends the same fiber type (don’t mix single-mode and multimode).
Fiber Types & Jacket Colors
| Type | Jacket | Core / Mode | Typical Reach |
|---|---|---|---|
| OM1 | Orange | 62.5/125 multimode | 1G ~275 m (legacy) |
| OM2 | Orange | 50/125 multimode | 1G ~550 m |
| OM3 | Aqua | 50/125 laser-optimized | 10G ~300 m |
| OM4 | Aqua | 50/125 laser-optimized | 10G ~400 m |
| OM5 | Lime | 50/125 wideband MM | SWDM multi-lane |
| OS2 | Yellow | 9/125 single-mode | 10G+ many km |
Jacket colors are conventions, not guarantees — always verify the print legend on the cable.
Cisco Port LED Guide
Catalyst port LED in the default STATUS mode.
Off — no link / nothing connected, or port admin-down (shut).
Solid green — link up, no traffic.
Blinking green — link up with activity. The healthy "traffic flowing" state.
Solid amber — disabled / err-disabled or STP blocking. A brief amber on a new connection is normal during spanning-tree.
Alternating green/amber — link fault, faulty device, or duplex mismatch.
The MODE button changes what the port LEDs show:
STATlink / activity (default)
SPEEDblink pattern indicates 10 / 100 / 1000
DUPLXgreen = full duplex, off = half
PoEgreen = delivering; blinking amber/green = denied or fault
SPEEDblink pattern indicates 10 / 100 / 1000
DUPLXgreen = full duplex, off = half
PoEgreen = delivering; blinking amber/green = denied or fault
Quick read: blinking green = healthy with traffic; solid amber = shut or err-disabled (check show interface); alternating = physical / duplex fault. System SYST LED green = OK.
Cable Run Converter
Feet ↔ meters. Type in either box.
Max copper Ethernet run: 100 m (328 ft) end to end (~90 m permanent link + patch cords).