1.5 Compare and contrast transmission media and transceivers
Connector Types
📘CompTIA Network+ (N10-009)
What Is an RJ45 Connector?
RJ45 (Registered Jack 45) is an 8-pin, 8-position connector used for Ethernet networking.
It is the standard connector used on twisted-pair copper cables, such as:
- Cat5e
- Cat6
- Cat6A
- Cat7
- Cat8
These cables connect computers, switches, routers, servers, and other network devices in an IT environment.
The RJ45 connector is part of the 8P8C (8 Positions, 8 Contacts) connector family, meaning it has eight separate metal contacts that transmit and receive electrical signals.
Where the RJ45 Connector Is Used in IT Environments
In real IT networks, RJ45 connectors are used to connect:
- Computers to network switches
- Switches to routers
- PoE (Power over Ethernet) devices such as IP cameras and VoIP phones
- Access points to wired backhaul
- Servers to switches in data centers
- Patch panels to switches using patch cables
- Network interface cards (NICs) to the wired network
RJ45 connectors are essential anywhere Ethernet communication is required.
Key Characteristics of the RJ45 Connector
1. 8P8C Design
- 8 pins, 8 positions
- Each pin carries part of the Ethernet signal
- Supports Fast Ethernet, Gigabit Ethernet, 10G Ethernet, and higher (depending on cable type)
2. Compatible Cables
RJ45 connectors terminate twisted-pair copper cables, including:
| Cable Type | Typical Use |
|---|---|
| Cat5e | 1 Gbps Ethernet |
| Cat6 | 1–10 Gbps Ethernet |
| Cat6A | Up to 10 Gbps, better shielding |
| Cat7/Cat8 | Data centers, high-speed connections |
3. Supports T568A and T568B Wiring Standards
When attaching an RJ45 connector to a cable, one of two wiring standards must be used:
- T568A
- T568B
Both define the order of wire colors inside the connector.
Network+ exam tip:
Both standards work, but T568B is more common in the U.S.
A cable using the same standard on both ends is called a straight-through cable.
4. Used for Ethernet Link Types
Different Ethernet standards use RJ45 connectors:
| Ethernet Standard | Speed | Notes |
|---|---|---|
| 10BASE-T | 10 Mbps | RJ45 |
| 100BASE-TX | 100 Mbps | RJ45 |
| 1000BASE-T | 1 Gbps | RJ45 (all 4 pairs used) |
| 10GBASE-T | 10 Gbps | Cat6+, RJ45 |
How RJ45 Connectors Work (Simple Explanation)
RJ45 connectors transmit network data using electrical signals sent across twisted wire pairs.
For example:
- One pair transmits data
- Another pair receives data
- In Gigabit and 10 Gigabit Ethernet, all four pairs carry data
Twisting the pairs helps reduce electromagnetic interference (EMI) and crosstalk, improving performance.
RJ45 in Patch Panels and Network Racks
In IT racks, RJ45 connectors are used to:
- Connect patch panel ports to switches
- Connect servers or devices to rack-mounted switches
- Extend structured cabling from wall jacks to networking equipment
This is essential for organized cable management in businesses and data centers.
Power over Ethernet (PoE) and RJ45
RJ45 connectors can deliver both:
- Data
- Electrical power
This is known as Power over Ethernet (PoE) and is used for:
- Wireless access points (WAPs)
- VoIP phones
- IP security cameras
- PoE lighting systems
PoE eliminates the need for separate power adapters.
Types of RJ45-Related Cables for the Exam
1. Straight-Through Cable
- Same wiring standard (T568A→T568A or T568B→T568B)
- Used to connect different device types
Example: computer → switch
2. Crossover Cable
- Different wiring standards (T568A→T568B)
- Used to connect similar devices
Example: switch → switch (older devices without Auto-MDI/MDIX)
Most modern devices automatically detect crossover needs.
3. Shielded (STP) vs Unshielded (UTP) Connectors
RJ45 connectors come in two forms:
| Type | Where Used | Purpose |
|---|---|---|
| UTP RJ45 | Standard office networks | Basic Ethernet |
| STP RJ45 | Areas with high interference | Extra shielding |
If the cable is shielded, the RJ45 connector must also support grounding.
RJ45 Connector Pinout (Exam Important)
RJ45 uses eight pins, numbered 1 through 8.
T568B (most common) pinout:
| Pin | Wire Color | Purpose |
|---|---|---|
| 1 | White/Orange | Transmit + |
| 2 | Orange | Transmit – |
| 3 | White/Green | Receive + |
| 4 | Blue | Not used in 100 Mbps / used in PoE & Gigabit |
| 5 | White/Blue | Not used in 100 Mbps / used in PoE & Gigabit |
| 6 | Green | Receive – |
| 7 | White/Brown | Used in Gigabit/PoE |
| 8 | Brown | Used in Gigabit/PoE |
Common RJ45 Issues (Useful for Troubleshooting Questions)
1. Bad Crimping
Loose or misaligned pins cause network drops.
2. Broken Clip
The connector won’t lock into the port properly.
3. Incorrect Wiring Standard
Using A on one end and B on the other unintentionally creates a crossover cable.
4. Interference
Using unshielded connectors in high-EMI areas reduces performance.
5. Wrong Cable Category
Using Cat5e for 10G speeds will fail.
How the RJ45 Connector Appears on the Exam
Expect questions asking about:
- Identifying the RJ45 visually
- Knowing it is used for Ethernet over twisted-pair
- Understanding 8P8C
- Knowing the difference between T568A and T568B
- Matching RJ45 to Cat5e/Cat6/Cat6A cables
- Recognizing typical uses (switches, routers, servers)
- Understanding straight-through vs crossover cables
- Knowing that RJ45 is used for PoE delivery
Summary: What You Must Know for the Network+ Exam
- RJ45 is an 8P8C connector used for Ethernet networking.
- Works with twisted-pair copper cables: Cat5e, Cat6, Cat6A, etc.
- Supports speeds up to 10G Ethernet (with the right cable).
- Uses T568A/B wiring standards.
- Common in switches, routers, computers, servers, and patch panels.
- RJ45 connectors can deliver PoE power.
- Straight-through = different devices
Crossover = same devices (older networks) - Gigabit and faster Ethernet use all four twisted pairs.
