Network cables and Ethernet: what you plug in and why it matters
In short: Ethernet cables connect devices to switches and routers. Copper twisted-pair cables (Cat5e, Cat6, Cat6A) work up to 100 metres; fibre carries data much further using light. A wired connection is usually faster and steadier than Wi-Fi.
The simple idea
Wi-Fi gets most of the attention, but almost every network still depends on cables. Your router connects to the internet with one, office desks connect to switches with them, and the switches connect to each other with them. The standard for this kind of wired network is called Ethernet.
Copper twisted-pair cables
The everyday network cable contains eight thin copper wires twisted into four pairs. The twisting cancels out electrical interference. The plug at each end is called RJ45: it looks like a slightly wider phone plug and clicks into place.
Cables come in categories ("Cat"). A higher number means it is built to carry faster signals:
| Category | Typical speed | Good for |
|---|---|---|
| Cat5e | 1 Gbps up to 100 m | Homes and older offices |
| Cat6 | 1 Gbps up to 100 m, 10 Gbps up to about 55 m | Most new installations |
| Cat6A | 10 Gbps up to 100 m | New offices, Wi-Fi 6/7 access points |
The magic number is 100 metres: the maximum length for a copper Ethernet run between two devices. Beyond that, signals become unreliable.
Fibre optic cables
Fibre carries data as pulses of light through a strand of glass thinner than a hair. It is not affected by electrical interference, it can run for kilometres, and it supports very high speeds. Companies use it between floors and buildings, and internet providers use it to bring "full fibre" broadband to homes. Fibre needs special connectors (such as LC) and small modules in the switch called transceivers (often SFP).
Power over the same cable
PoE (Power over Ethernet) sends electrical power along a copper network cable, so devices such as Wi-Fi access points, desk phones and security cameras need only one cable and no plug socket. The switch must support PoE.
Real-world example: the slow cable nobody noticed
An office moves to a faster internet connection but one manager's computer still feels slow. The speed test shows exactly 100 Mbps. The cause is an old, damaged cable under the desk: one of its pairs is broken, so the network card falls back to the older 100 Mbps standard. Replacing a five-metre patch cable fixes it instantly. When a wired device is stuck at exactly 100 Mbps, check the cable first.
Tips for choosing cables
- For new home or office cabling, choose Cat6 or Cat6A.
- Do not bend cables sharply, staple through them or run them alongside power cables for long distances.
- Label both ends. Future you will be grateful.
- For gaming, video calls or a home office, a cable is usually steadier than Wi-Fi: see Wi-Fi vs Ethernet.
Try this: on Windows, open Settings > Network > Ethernet and look at "Link speed". On a working Cat5e or better cable to a modern router you should see 1000 Mbps (1 Gbps).
Key takeaways
- Ethernet is the standard for wired networks; the common plug is RJ45.
- Copper cables (Cat5e, Cat6, Cat6A) work up to 100 metres.
- Fibre uses light and covers much longer distances.
- PoE sends power and data along one copper cable.
Original content written by Mohamed Fayas for FM TecHub. © 2026 FM TecHub. You're welcome to share a link to this page; please don't copy the text elsewhere without permission.