Choosing network cable: Cat 6A, Cat 7 or Cat 8 for offices and new builds

The short answer: Cat 6A on the floor, fibre for the backbone

For workstations, access points, cameras and other end devices, Cat 6A is the right choice today. It carries 10 Gbit/s over the full 100-metre channel and copes with the higher power demands of modern PoE devices. Equipment rooms, floors and buildings are best connected with fibre.

What matters is the whole link, not the label on the cable drum. Cabling usually outlasts several generations of switches and end devices. Recabling later is expensive and disruptive. That is why careful structured cabling design pays off before the first cable is pulled.

Cat 5e to Cat 8 compared

The category describes the frequencies a cable or component is designed for. The standards EN 50173 and ISO/IEC 11801 use classes for the finished link, for example Class EA for Cat 6A. The weakest component always decides: cable, outlet, patch panel and patch cords must match.

Cat 5e and Cat 6: for existing networks

Cat 5e handles Gigabit Ethernet over 100 metres and is found in many older buildings. Cat 6 manages 10 Gbit/s only over considerably shorter runs and under favourable conditions, because alien crosstalk between neighbouring cables limits the reach. Working legacy cabling need not be replaced at once, but neither category suits new installations.

Cat 6A: 10 Gbit/s over the full distance

Cat 6A is designed for 10GBASE-T over a 100-metre channel. That is up to 90 metres of installed cable plus up to 10 metres of patch cords across both ends. This comfortably serves access points with multi-gigabit ports and future devices. Cat 6A cables are thicker than older types, which matters for cable trays, conduit and back boxes.

Cat 7 and Cat 7A: the cable is not the link

Cat 7 and Cat 7A are defined in ISO/IEC 11801 for higher frequencies, but they use their own connectors such as GG45 or TERA instead of RJ45. Because practically all switches, access points and computers have RJ45 ports, Cat 7 installation cable is usually terminated with Cat 6A outlets and patch panels. The link then achieves Class EA, which is Cat 6A level. This proven approach is common in German-speaking countries, but it does not raise the data rate.

Cat 8: for short runs in the data centre

Cat 8 is designed for 25GBASE-T and 40GBASE-T, but only over channels of up to 30 metres. It is intended for switch-to-server connections within a row of racks. In the office, Cat 8 brings no benefit: workstation runs are often longer than 30 metres, and fibre is the established solution for high data rates between distributors.

Shielding: U/UTP, F/UTP or S/FTP

The part before the slash describes the overall shield of the cable, the part after it the shielding of the individual pairs. U stands for unshielded, F for foil and S for braid. TP means twisted pair.

• U/UTP: no shield and easy to work with, but relatively thick at Cat 6A. Common in the UK and the US.
• F/UTP: foil around all pairs. A good compromise between protection against interference, diameter and ease of installation.
• S/FTP: braid around the cable and foil around each pair. Typical for Cat 7 installation cable and very common in offices in Austria and Germany.

Shielded cables protect better against external interference and crosstalk between cables, for example in production halls or next to power cables. This only works if the shield runs continuously through outlet, patch panel and patch cord and the rack is properly connected to the equipotential bonding. An interrupted shield throws the advantage away.

PoE and heat: why conductor size matters

Power over Ethernet supplies access points, cameras, phones or card readers through the data cable. IEEE 802.3bt allows up to 90 watts at the switch port, of which around 71 watts reach the device after losses in the cable. The current heats the conductors, and in dense cable bundles this heat adds up. Higher temperature increases attenuation and can, in unfavourable cases, reduce the permissible link length.

• Cables with thicker conductors, such as AWG 23 or AWG 22, have lower resistance and heat up less.
• Avoid large, tightly packed bundles, especially in insulated areas and poorly ventilated shafts. ISO/IEC TS 29125 gives guidance on bundle sizes.
• Avoid copper-clad aluminium (CCA) cable: it does not meet structured cabling standards and heats up more under PoE load.
• Choose PoE-rated connectivity so that plugging and unplugging under load does not damage the contacts.

Fire performance: cables under the EU Construction Products Regulation

In the EU, cables permanently installed in buildings count as construction products. Under the Construction Products Regulation (CPR), their reaction to fire is classified from Aca to Fca, with additional classes for smoke production (s), flaming droplets (d) and acidity (a). The class is stated in the manufacturer's declaration of performance and on the label of the drum or coil.

Which class a building requires is not decided by the network designer but by building regulations and the fire safety concept, for example for escape routes or publicly accessible areas. Clarify the requirement early with the architect, fire safety planner or property manager. Halogen-free cable jackets are standard in offices anyway, because they release fewer corrosive gases in a fire.

Checklist for offices and new builds

1. Define the outlets per workstation and plan spare capacity for access points, cameras, card readers and printers.
2. Specify Cat 6A (Class EA) for floor cabling, using Cat 6A cable or Cat 7 cable with Cat 6A connectivity.
3. Decide on a shielding concept and implement it consistently, including equipotential bonding in the equipment room.
4. Match conductor size and bundle sizes to the planned PoE load.
5. Clarify the required fire class before ordering and state it in the tender.
6. Connect distributors and buildings with fibre. Our article on single-mode and multimode explains which fibre fits.
7. Have every link tested and make sure you receive the test reports together with plans and labelling.

Conclusion: plan for the link, not the label

For most offices, practices, shops and new builds, Cat 6A cabling with a fibre backbone is a solid foundation for the years ahead. Cat 7 installation cable is a good option, provided it is clear that the link reaches Cat 6A level. Cat 8 belongs in the data centre. If you are planning a new build, a refurbishment or an office move, Q-entra supports you with structured cabling from design to test report.