What do Cat5e, Cat6 and Cat6A mean?

“Cat” is short for category. It describes a set of electrical performance requirements for the cabling, including how well signals are kept apart and how much they weaken along the route. It is not a measurement of your internet speed.

Ethernet is the technology carrying data over the link. The familiar clip-in plug is commonly called RJ45; the connector used on these everyday network leads has eight positions and eight contacts, often written as 8P8C.

Technical background: Gigabit over Cat5; Cat6 and 10GBASE-T testing; cable-category history; Ethernet Alliance on 2.5/5 Gigabit.

MHz is not Mbps

A cable frequency rating, such as 250 MHz for Cat6 or 500 MHz for Cat6A, describes the frequency range over which its performance is specified. Mbps and Gbps describe data rates. They are related through the Ethernet signalling system, but you cannot convert one into the other with a simple multiplier.

More on frequency and data rate.

A cable is one part of a system

Higher-category cable cannot make a lower-rated socket meet a higher specification. Patch leads, connectors, workmanship and the fixed cable all affect the finished channel. For a specified performance level, ask for the installation to be tested against that requirement.

Jacket colour is not a category standard. A blue cable is not automatically Cat5e, and a purple cable is not automatically Cat6A. Read the markings and documentation.

What does “up to 100 metres” include?

The channel is the complete passive cable connection between two active network ports. In a conventional structured-cabling design, its 100-metre allowance includes up to 90 metres of fixed wiring plus a combined 10 metres of patch leads. It is not 100 metres inside the walls with unlimited extra leads at each end.

Source: Fluke Networks on permanent links and patch cords.

When the route gets longer or leaves the building

Measure the actual cable route, including rises, drops and the path around rooms. A garden office 20 metres from the house may need considerably more than 20 metres of cable.

For long routes or links between buildings, have the connection designed for the site. The decision may involve fibre, a wireless bridge or suitably specified external cabling. Check weather exposure, the cable sheath, mechanical protection and how the equipment will be powered. Choosing a higher Cat number does not settle those questions.

Twisted pairs and shielding, made visible.

A typical Ethernet cable of the types covered here contains four twisted pairs: eight insulated conductors in total. Twisting helps the signalling system resist interference. Some designs add foil or braid screens. The category describes performance; the shielding code describes construction.

Read the letters either side of the slash. The first part describes the screen around the whole cable bundle; the second describes the pairs. U means unshielded, F means foil and S means braid. TP means twisted pair.

Original realistic illustrations, created for this guide. Layers are opened out to make them visible; exact materials, separators and dimensions vary by product. These are explanatory cutaways, not termination instructions.

What stripped cable looks like in real photographs

Real foil is thin and crinkles when pulled back. Braid looks like a woven mesh. These photographs show those textures on actual cable samples.

Other combinations exist, including U/FTP, with individually foil-screened pairs and no overall screen. Cat6A, for example, is available in both shielded and unshielded constructions. Do not use a picture of one cable as proof that every cable in its category looks that way.

Shielded cabling needs suitable connectors and the correct termination, bonding and earthing arrangements for the system. More metal around a cable is not a substitute for a well-planned route and good installation.

References: shielding designations; why shield continuity matters.

References: solid and stranded conductors; copper-clad aluminium explained.

PoE: one cable, two jobs.

Power over Ethernet allows compatible equipment to receive data and electrical power through the same network connection. It is commonly used for WiFi access points, IP cameras and desk phones. A PoE switch or injector supplies power; the receiving device must support the appropriate system.

The category number alone does not tell you how much power a device can receive. Check the device’s required PoE type, the switch or injector’s supported output, the switch’s total power budget and the installed channel. Passive power injectors are not interchangeable with every standards-based PoE device.

Technical background: Fluke Networks’ PoE installation guide. Follow the actual equipment and cabling manufacturers’ instructions for the installation.

A slow connection needs a few checks.

If a link is slower than expected, establish where the limit is before buying a higher-category lead. These checks help narrow the problem; they do not replace certification of installed wiring.

1. Check the ports at both ends. Confirm the supported Ethernet speeds for the exact router, switch and device. A television or other appliance may have a slower port than your computer.
2. Read the negotiated link speed. The device’s network settings or managed switch can show whether it connected at 100 Mbps, 1 Gbps or another rate. This is different from an internet speed-test result.
3. Try a known-good copper patch lead. Change one part at a time. Reseat the connectors and look for broken latches, damage or plugs that do not fit securely.
4. Simplify the route where practical. A direct comparison with the same equipment can help separate a patch lead from wall wiring, sockets, couplers or intermediate network equipment.
5. Investigate a persistent 100 Mbps link. Common 100BASE-TX Ethernet uses two pairs, whereas 1000BASE-T needs four. Pair faults are one possible reason for a lower speed, but port capabilities and settings also need checking.
6. Test the installed link properly. A basic continuity tester can identify some wiring faults. It cannot prove that the complete channel meets Cat6A performance or will reliably support the intended Ethernet application.

For an access point, the wired link is only part of the story. Wireless coverage, interference and device capabilities still matter. Our WiFi & RF guides explain that side of the connection. If the symptom is a freezing television app, see streaming apps stuttering for checks that also consider the app and device.