Understanding Ethernet cables — a guide to wired networking

Understanding Ethernet cables - a guide to wired networking

This comprehensive guide aims to provide you with the knowledge needed to make informed decisions when it comes to selecting and utilizing Ethernet cables.


In today’s digital world, connectivity is vital for both personal and professional endeavours. Whether it is for media streaming, online gaming or internet surfing, data transmission from the internet to your device takes place.

Ethernet cable connectivity (vs. wireless/Wi-Fi connectivity) plays a crucial role in establishing reliable connections for data transmission. Whether you are setting up a home network, upgrading small office infrastructure, or seeking efficient internet connectivity, understanding the different types, categories, and features of Ethernet cables is essential.

This post will discuss what an Ethernet cable is, how it fits in with modems, routers and switches, types of Ethernet cables, Ethernet cable connectors and choosing the right Ethernet cable. It also features a section on inspecting Ethernet cables and, as a bonus, the wiring diagram to create your own Ethernet cables.

What is an Ethernet cable?

An Ethernet cable, also known as a network cable or LAN cable, is a physical cable used to connect devices such as computers, routers, switches, and modems to establish a wired network connection. Nowadays, this connection is more likely to be indirect to a switch, or directly into a router connected to the internet.

Ethernet cable with RJ-45 plugs

An example of an Ethernet cable with RJ-45 plugs at both ends.

Ethernet cables allow for the transmission of data packets using Ethernet technology, providing faster and more stable internet connectivity compared to wireless networks.

Modems, routers and switches

In order to understand Ethernet cables better, one might need to understand the functions of modems, routers and switches.

Modems, routers and switches are all networking devices, but they serve different functions in a network. A modem connects a local network to the internet, a router manages network traffic and enables communication between devices in the network and the internet, and a switch facilitates communication between devices within a local network.

In many home and small office setups, these functionalities are often combined into a single router that incorporates modem, routing, and switching capabilities. For home and small business use, network switches are often connected to a router to extend the number of connected devices to the network.


A modem is a device that connects your home or office network to the internet service provider (ISP). It serves as a bridge between your local network and the ISP’s network. They typically have ports for connecting to your ISP via a coaxial cable, DSL line, or fibre optic cable.


A router is a device that connects multiple devices within a network. It acts as a central hub for a local network and manages the flow of information between different devices, both within your network and between your network and the internet.

Wired networking: Ethernet slots on a router

This is a network router which is connected to a modem. The open ports are to connect devices using RJ-45 Ethernet plugs. This switch has four open ports to connect devices.


A switch is a networking device that allows multiple devices within a local network to communicate with each other. It provides various Ethernet ports to connect devices via Ethernet cables.

Types of Ethernet Cables

There are some factors to consider when getting a new Ethernet cable. Not all Ethernet cables are the same. While some Ethernet cables transfer data faster than others (latency), some can transfer more data at a time (bandwidth), and others can transfer data over longer distances. There are also significant price differences between types of Ethernet cables.

In its broadest sense, Ethernet cables can be divided into unshielded and shielded cables — both commonly used. The primary difference between these two types of cables lies in their construction and level of protection against electromagnetic interference (EMI) and crosstalk. Ethernet cables are also categorised based on their performance and capabilities.

Unshielded Twisted Pair (UTP) Ethernet cables

UTP cables are the most common type of Ethernet cable used today. They consist of twisted pairs of copper wires enclosed in a plastic sheath. Each wire pair is twisted together to reduce interference between adjacent pairs. UTP cables are suitable for most residential and office environments where EMI is not a significant concern.

Unshielded Twisted Pair (UTP) Ethernet cable

Unshielded Twisted Pair (UTP) Ethernet cable. Image by Agott (CC-BY-SA)

Shielded Twisted Pair (STP) Ethernet cables

STP cables, similar to FTP (Foiled Twisted Pair), have an additional layer of shielding to provide better protection against EMI and crosstalk. The shielding helps to prevent external interference from affecting the signal quality and also reduces the emission of electromagnetic radiation from the cable. STP cables are commonly used in larger networks and/or industrial settings.


The choice between UTP and STP cables depends on the specific requirements and environmental factors of the network installation. UTP cables are generally more cost-effective, flexible, and easier to install. They work well in most residential and small office environments where EMI is minimal.

On the other hand, STP cables offer better protection against EMI and are suitable for environments with higher levels of electrical noise and interference. Large servo motors, generators, etc. will contribute to EMI. STP ethernet cables tend to be more expensive than UTP cables.

Ethernet cable categories (CATs)

Both UTP and STP cables are available in various categories (e.g., CAT 5e, CAT 6, CAT 6a, etc.), which determine their maximum data transmission speeds and performance capabilities.

The most commonly used categories are CAT5e, CAT6, CAT6a, and CAT7. CAT7a and CAT8 cables are also available. The Ethernet cable category determines factors such as bandwidth, transmission speed, and maximum cable length.

Category Max. Data Rate Max distance
(m / ft)
CAT1 1 Mbps 100 / 328 low, < CAT2
CAT2 4 Mbps 100 / 328 > CAT1
CAT3 10 Mbps 100 / 328 > CAT2
CAT4 16 Mbps 100 / 328 > CAT3
CAT5 100 Mbps 100 / 328 > CAT4
CAT5e 1 Gbps 100 / 328 > CAT5
CAT6 1 Gbps 100 / 328 > CAT5e
CAT6a 10 Gbps 100 / 328 > CAT6
CAT7 10 Gbps 100 / 328 > CAT6a
CAT7a 10 Gbps 100 / 328 > CAT7
CAT8 25 Gbps 30 / 98 > CAT7a
CAT8a 40 Gbps 30 / 98 high, > CAT8

Higher categories offer greater bandwidth and frequency capabilities, resulting in faster data transmission rates. Higher-category cables also tend to be more expensive and some are only indicated to be used over shorter distances (e.g. 30 instead of 100 meters).

The maximum cable length varies depending on the category, with 100 meters being the standard for most Ethernet cables. CAT8 and CAT8a Ethernet cables are indicated to be used at 30 meters / 98 feet). Cables that are longer than their indicated lengths will experience an increase in latency.

Ethernet cable connectors

RJ-45 (or RJ45) connectors are commonly used for Ethernet cables, allowing easy connection and compatibility with most devices.

RJ-45 crimp connectors plug

RJ-45 crimp connectors plug used in most Ethernet cables.

RJ-45 plugs are connected in a specific way to the wiring of the cable using a crimp tool. The plug can be used as is, or a sheet/shield/cover can be added for more protection and durability. Various versions of connector protection are available.

Choosing the right Ethernet cable

At the time of writing, most home and small business networks will function optimally when using CAT5 or CAT6 Ethernet cables. To choose the optimal Ethernet cable for your network requirements, the following steps can be followed.

Step 1 Consider environmental factors

Important environmental factors include temperature and interference from other electronic devices.

If you plan to install Ethernet cables in a challenging environment, Shielded Twisted Pair (STP) Ethernet cables are more durable and allow for less interference. Unfortunately, STP Ethernet cables are more rigid and more difficult to install around corners.

Step 2 Consider the networking needs (most important)

Determine the required bandwidth and transmission speed based on the network setup

Fibre optics, the fastest internet available for most people, only need about 9.4Gbps to be at full speed — so a CAT6a Ethernet cable would be perfectly fine. Networks with only 1Gbps bandwidth could be handled by a CAT6 Ethernet cable.

Also, consider the maximum bandwidth of the router and switches in the network.

Step 3 Consider the required length of the cable

Most Ethernet cables will perform optimally up to a discharge of 100 meters / 328 feet. CAT8 and CAT8a cables are only indicated to be used at a maximum length of 30 meters / 98 feet.

Step 4 Consider installation, maintenance and cable management

Unshielded Twisted Pair (UTP) cables tend to be more flexible, allow more bending and are easier to work with. Proper cable management will ensure neat and organised cable routing to avoid damage and interference.

Step 5 Consider future-proofing

If you anticipate future upgrades or advancements in your network infrastructure, opting for a higher-category cable may provide better longevity and compatibility.

Step 6 Consider budget

Using higher-than-required category cables would work well, but it also costs a lot more and is likely able to handle quadruple (or more) the speeds coming from ISPs.

Inspecting Ethernet cables

Eethernet cables that are worn down and/or damaged will cause slower data transmission and speed or will not function at all. Cables that are bent beyond their recommended bending angle will also perform sub-optimally.

Check for physical damage, loose connectors, or other signs of wear and tear. Periodically test the cables for continuity, signal integrity, and potential issues.

Power over Ethernet (PoE)

The maximum cable lengths indicated earlier are more important for PoE. The Voltage will start to drop significantly in Ethernet cables longer than their recommended maximum cable length.


Whether it’s for home, office, or industrial applications, a well-chosen Ethernet cable can provide fast and stable connectivity, ensuring smooth data transmission and optimal network performance.

Ethernet cables remain a reliable and efficient solution for establishing wired network connections. Understanding the various types, categories, cost differences and features of Ethernet cables is crucial in selecting the right cable for your networking needs.

Leave a Reply

Your email address will not be published. Required fields are marked *