CompTIA Network+ Network Fundamentals Foundational

Cable Connector Types — Copper, Fiber, Coax

Every connector CompTIA Network+ (N10-009) shows in exam images: RJ45, RJ11, F-type, BNC, SC, LC, ST, MTRJ, MPO, LC-APC vs LC-UPC. What each pairs with and the one-line 'how to tell them apart' rule.

Quick summary

The image-recognition side of Network+: recognize a connector by shape at a glance. RJ45 is 8-pin twisted pair; RJ11 is 4/6-pin phone; F-type is coax with a threaded barrel; BNC is coax with a bayonet twist-lock.
Fiber: **SC** = square 'stick-and-click'; **LC** = the small square with a latch (half SC); **ST** = round bayonet 'stab-and-twist'; **MTRJ** = one connector for both fibers; **MPO** = 12+ fibers in one ribbon.
APC vs UPC — green vs blue. APC has an 8° angled endface (lower return loss). Never mate APC to UPC — physical mismatch = permanent damage.

Copper connectors

Connector	Pins	Cable	Where you’ll see it
RJ45	8	Cat5/5e/6/6a/7/8 UTP-STP	Every Ethernet drop.
RJ11	4 or 6	Twisted pair (2 or 3 pair)	POTS phone, DSL.
F-type	Center + threaded barrel	RG-6, RG-59 coax	Cable modems, satellite TV.
BNC	Center + bayonet twist	RG-58, RG-59 coax	Legacy 10BASE-2, some security cameras.
DB-9 / RS-232	9	Serial	Cisco console (legacy).
USB-A / USB-C / Micro-USB	—	—	Modern console access on switches/routers.

How to tell RJ45 from RJ11 at a glance: RJ45 is wider (8 conductors). RJ11 is narrower (4-6). If you can only fit two pairs, it’s RJ11.

Fiber connectors — the four the exam expects

Connector	Shape / Mount	Size
SC — Subscriber Connector	Square. Push-pull, “stick and click”.	~9 mm ferrule. Large.
LC — Local Connector	Square with a small RJ45-style latch. Push-pull.	~4.5 mm ferrule. Half the size of SC.
ST — Straight Tip	Round with a bayonet twist-lock. “Stab and twist”.	Older tech. Legacy MMF.
FC — Ferrule Connector	Round with a threaded screw-on barrel.	Test equipment, precise alignment.
MTRJ — Mechanical Transfer RJ	One connector body holds both TX + RX fibers. RJ-style latch.	Uncommon.
MPO / MTP	Rectangular. Holds 12 or 24 fibers in a ribbon.	40 GbE / 100 GbE, spine-leaf DC.

How to tell SC from LC: LC is half the size of SC. If it clicks with a latch like RJ45, it’s LC. If it slides in and clicks with no lever, it’s SC.

APC vs UPC — the color code that saves cables

Fiber endfaces are polished two ways:

UPC (Ultra Physical Contact) — flat endface. Blue connector body.
APC (Angled Physical Contact) — 8° angled endface. Lower return loss. Green connector body.

If you plug an APC into a UPC port, the angled ferrule crashes into the flat one and physically damages both. Blue mates blue, green mates green. Never mix.

Single-mode vs multi-mode (color code)

You can spot cable type on the exam by the jacket color:

Yellow jacket → single-mode (SMF, ~9 µm core, up to ~40 km).
Orange jacket → OM1 or OM2 multi-mode (50–62.5 µm core).
Aqua jacket → OM3 or OM4 laser-optimized MMF.
Erika violet / lime → OM5 wideband MMF.

Coax types the exam mentions

RG-6 — thick, F-type connector, TV / cable modem.
RG-59 — thinner, older CCTV.
RG-58 — the old 10BASE-2 “thinnet” cable. BNC connectors. Dead in modern networking.

Common exam traps

APC vs UPC = green vs blue. Miss this and you’ll miss the picture-based question.
MPO/MTP is what plugs into a 40G/100G port on a spine-leaf switch. If the exam says “one connector, twelve fibers”, it’s MPO.
RJ45 shielded (STP) uses drain wire termination — the connector has a metal shield around it. Not visually different in a small image; if the question says “office with heavy EMI”, pick shielded.
BNC ≠ Ethernet in modern networks. If you see BNC on the exam and Ethernet is the answer, it’s a legacy scenario or a distractor.
F-type is threaded, BNC is twist-lock. Both are coax. Threaded barrel = F-type.

Cheat strip

RJ45  8-pin  Cat5+ UTP     — every LAN drop
RJ11  4/6-pin              — POTS / DSL
F-type threaded             — TV / cable modem
BNC   bayonet               — legacy coax
SC    square push-pull      — SMF/MMF, larger
LC    square with latch     — SMF/MMF, half-size SC (modern)
ST    round bayonet         — legacy MMF
MPO   ribbon, 12+ fibers    — 40G / 100G
APC   green   angled 8°     — never mate to UPC
UPC   blue    flat          — never mate to APC

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