Networking

Ethernet (RJ-45)

Ethernet cables use twisted pair copper wiring with an RJ-45 connector to provide wired network connectivity. They are the backbone of local area networks (LANs) and are used to connect computers, switches, routers, and other network devices. Ethernet cables follow the IEEE 802.3 standard and come in various categories that determine their maximum speed and bandwidth.

Primary Use

Networking & Data Transfer

Reference Image

Ethernet (RJ-45) cable and connector

Key Features

  • RJ-45 connector with 8 pins (4 twisted pairs)
  • Clear plastic connector housing with a locking clip/tab
  • Wider than a phone cable (RJ-11) - a common point of confusion
  • Available in categories: Cat5, Cat5e, Cat6, Cat6a, Cat7, Cat8
  • Maximum cable length of 100 meters (328 feet) for most categories
  • Wiring standards: T-568A and T-568B color-coded pin configurations
  • Can be straight-through (device to switch) or crossover (device to device)
  • Shielded (STP) and unshielded (UTP) variants available

Variants & Standards (6)

Cat5 100 Mbps

Legacy standard, largely obsolete

  • - 100 MHz bandwidth
  • - Not recommended for new installations
Cat5e (Enhanced) 1 Gbps

Improved Cat5 with reduced crosstalk

  • - 100 MHz bandwidth
  • - Most common in older installations
  • - Supports Gigabit Ethernet
Cat6 10 Gbps (up to 55m)

Higher performance with tighter twisting and separator

  • - 250 MHz bandwidth
  • - Internal spline separator
  • - Thicker cable jacket
Cat6a (Augmented) 10 Gbps (full 100m)

Extended Cat6 supporting full 100m runs at 10 Gbps

  • - 500 MHz bandwidth
  • - Improved shielding
  • - Thicker and less flexible
Cat7 10 Gbps

Shielded cable for high-performance networks

  • - 600 MHz bandwidth
  • - Fully shielded (each pair + overall)
  • - GG45 or TERA connectors (can use RJ-45)
Cat8 25/40 Gbps

Data center grade, highest performance

  • - 2000 MHz bandwidth
  • - 30-meter maximum length
  • - Designed for data centers

Quick ID Tips

1 Look for the clear plastic RJ-45 connector - it is wider than a phone jack (RJ-11)
2 Has a plastic locking clip/tab on one side that clicks when inserted
3 8 gold-colored metal contacts visible through the clear connector
4 Cable is typically round and thicker than a phone cord
5 Often color-coded by category: blue is most common for patch cables

A+ Exam Notes

Know the difference between RJ-45 (Ethernet) and RJ-11 (phone) connectors
T-568B is the most common wiring standard in commercial installations
Crossover cables swap transmit and receive pairs - used for direct device-to-device connections
Cat5e is the minimum recommended for Gigabit Ethernet
Cat6a supports 10 Gbps at the full 100-meter distance
PoE (Power over Ethernet) can deliver both data and electrical power over Ethernet cables

At a Glance

Type Networking
Variants 6
Key Features 8
Exam Tips 6