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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

ConnectorPinsCableWhere you’ll see it
RJ458Cat5/5e/6/6a/7/8 UTP-STPEvery Ethernet drop.
RJ114 or 6Twisted pair (2 or 3 pair)POTS phone, DSL.
F-typeCenter + threaded barrelRG-6, RG-59 coaxCable modems, satellite TV.
BNCCenter + bayonet twistRG-58, RG-59 coaxLegacy 10BASE-2, some security cameras.
DB-9 / RS-2329SerialCisco console (legacy).
USB-A / USB-C / Micro-USBn/an/aModern 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 exam expects

ConnectorShape / MountSize
SC: Subscriber ConnectorSquare. Push-pull, “stick and click”.2.5 mm ferrule. Large.
LC: Local ConnectorSquare with a small RJ45-style latch. Push-pull.1.25 mm ferrule. Half the size of SC.
ST: Straight TipRound with a bayonet twist-lock. “Stab and twist”.Older tech. Legacy MMF.
FC: Ferrule ConnectorRound with a threaded screw-on barrel.Test equipment, precise alignment.
MTRJ: Mechanical Transfer RJOne connector body holds both TX + RX fibers. RJ-style latch.Uncommon.
MPO / MTPRectangular. 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, you get high insertion loss and back-reflection, and the mismatched end faces can be physically damaged. 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 to 62.5 µm core).
  • Aqua jacket → OM3 or OM4 laser-optimized MMF.
  • Lime green jacket → OM5 wideband MMF. (Erika violet is sometimes used for OM4, mainly in Europe.)

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

  1. APC vs UPC = green vs blue. Miss this and you’ll miss the picture-based question.
  2. 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.
  3. 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.
  4. 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.
  5. 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
← Previous topic

Common Ports and Protocols: N10-009 Reference Table

Every port and protocol CompTIA Network+ (N10-009) expects you to memorize. Grouped by category with TCP/UDP, the encrypted alternative where one exists, and the one thing most students forget.

Next topic →

Business Continuity Metrics: RPO, RTO, MTBF, MTTR + Site Types

The four continuity metrics on CompTIA Network+ (N10-009): RPO, RTO, MTBF and MTTR, plus cold, warm and hot sites and how a real DR runbook uses them.

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Every physical and logical topology CompTIA Network+ (N10-009) tests: bus, ring, star, mesh, hybrid, point-to-point, hub-and-spoke, three-tier, spine-leaf. Diagrams, trade-offs, real-world use.

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