Basic Network Cabling Guide: What Cables Do You Need?

Cable is the cheapest component in a network and the most expensive one to replace.

Every other piece of equipment can be swapped in an afternoon. A switch fails, you unrack it and install another. A router reaches end of life, you replace it over a weekend. But the cable running through a wall, above a ceiling, and down a riser stays where it is for fifteen years, because pulling it out means opening the building.

That asymmetry should drive every purchasing decision in this article. When choosing network cables, buy for the wall rather than for today's requirement.

The Categories That Actually Matter

The specifications have proliferated, and several exist mainly for marketing. The ones that matter in practice:

• Cat5e. Supports gigabit speeds to the full 100-metre distance. Still perfectly adequate for ordinary desktop connections, and it will run 2.5 and 5 gigabit in many real installations. Cheap and thin, which makes it easy to route.
• Cat6. Supports gigabit to 100 metres, and 10 gigabit over shorter distances. Thicker and stiffer than Cat5e. The sensible default for new installations.
• Cat6a. Supports 10 gigabit to the full 100 metres. Noticeably thicker, harder to work with, and more expensive. The right choice for permanent runs you expect to keep for a decade or more.
• Cat8. Supports 25 and 40 gigabit over very short distances — around 30 metres. Designed for data centre connections between adjacent racks, and irrelevant to office cabling.

Cat7 deserves a specific warning. It is not recognised by the American standards body that defines structured cabling, and in its original form it requires connectors that are incompatible with standard Ethernet ports. Cable sold as "Cat7" with ordinary RJ45 connectors is not genuinely meeting that specification. In practice, buy Cat6a instead — it is a real standard with real testing behind it.

The Cat6 Ten-Gigabit Caveat

This catches people out, and the marketing does not help.

Cat6 supports 10 gigabit, but not across a full-length run. The reliable distance is substantially shorter than 100 metres — commonly cited as somewhere between 37 and 55 metres depending on how much interference comes from neighbouring cables in the same bundle.

That last factor is the important one. A single Cat6 cable in open air performs better than the same cable in the middle of a tightly bundled tray of forty others, because of interference between adjacent cables. Installation conditions genuinely affect the result.

If 10 gigabit to the desk is a realistic requirement within the lifespan of the installation, specify Cat6a and accept the extra cost and bulk. If it is not, Cat6 is a sound choice.

Solid or Stranded

Two constructions exist, and using the wrong one causes failures that appear months later.

• Solid conductor cable has a single solid copper wire per conductor. It carries signal better over distance and is designed to be terminated into punch-down connections — wall sockets and patch panels. It is stiff and does not tolerate repeated flexing; the conductors eventually crack.
• Stranded conductor cable uses many fine wires twisted together. It is flexible and tolerates movement, which makes it correct for patch leads between a wall socket and a computer, or between a patch panel and a switch.

The rule: solid for permanent runs, stranded for patch cables. Using stranded cable for an in-wall run degrades performance over distance. Using solid cable as a patch lead produces a cable that works until someone moves the desk, then intermittently fails in a way that takes hours to diagnose.

The Copper-Clad Aluminium Warning

This one matters for safety, not just performance.

A significant quantity of cheap cable sold online is not copper. It is aluminium with a thin copper coating, abbreviated CCA. It looks identical, costs considerably less, and is genuinely dangerous in certain applications.

Why it fails:

• Higher electrical resistance, producing more signal loss and reduced effective distance.
• Brittleness. Aluminium fractures where copper bends, so terminations fail and cables break inside walls.
• Poor connector contact, because the coating wears through.
• It does not meet the standards it claims to meet, and will fail certification testing.
• It is a fire risk under Power over Ethernet. Higher resistance means more heat, and PoE puts real current through these conductors. This is the serious one, and it is why building codes in many jurisdictions prohibit it.

How to avoid it: buy from established suppliers, check that the packaging states pure copper or bare copper conductor, and treat unusually cheap bulk cable with suspicion. A reel that costs half what everyone else charges is not a bargain you have discovered.

Shielded or Unshielded

Unshielded twisted pair is the default and is correct for the overwhelming majority of office installations. The twisting itself rejects interference effectively.

Shielded cable adds a foil or braid around the pairs, the whole bundle, or both. It is genuinely useful in specific environments:

• Industrial settings with heavy machinery.
• Cable runs that must travel alongside power cabling.
• Lift shafts and plant rooms.
• Installations near substantial radio transmitters.

The critical warning: shielded cable must be properly grounded at the correct point, using shielded connectors and shielded patch panels throughout. A shield that is not grounded, or grounded at both ends creating a current path, performs worse than no shield at all. Half-implemented shielding is a common and self-defeating expense.

For an ordinary office, unshielded is the right answer.

Fire Ratings

Cable jackets have fire classifications, and these are regulated rather than optional.

• Plenum rated cable is required in air handling spaces — the void above a suspended ceiling used for return air, for instance. It produces less smoke and toxic gas when burning.
• Riser rated cable is required in vertical shafts between floors, preventing flame spreading upward.
• General purpose cable is for ordinary horizontal runs within a single space.

Local regulations vary and this is one area where getting it wrong has consequences beyond network performance. If the installation is inside a building's structure, confirm the requirement with whoever signs off the work rather than guessing.

T568A, T568B, and the Death of the Crossover Cable

Two wiring standards define which colour goes to which pin. They differ only in swapping the orange and green pairs, and both work identically.

The only rule that matters: pick one and use it consistently throughout the installation. Mixing them within a single cable creates a crossover, and mixing them across an installation guarantees confusion later. T568B is the more common choice in most markets.

Crossover cables, which deliberately swap those pairs, are effectively obsolete. Virtually all modern equipment implements automatic detection, which senses the arrangement and adapts. Connecting two switches or two computers with an ordinary straight-through cable works. Keep one crossover cable in a drawer for very old equipment, and otherwise forget they exist.

The Hundred Metre Rule, Properly Explained

The maximum Ethernet distance is 100 metres, and that figure is routinely misunderstood.

It breaks down as 90 metres of permanent horizontal cable plus 10 metres total of patch cords at both ends combined. It is not 100 metres of in-wall cable plus patch leads on top.

Exceeding it produces frustrating intermittent behaviour rather than clean failure — the link negotiates, works most of the time, and drops under load. If a run must go further, the options are a switch partway along, or fibre.

Power over Ethernet Considerations

If cables will carry power to access points, phones, or cameras, additional factors apply:

• Pure copper is mandatory. See the warning above.
• Higher power standards generate real heat. Modern PoE can deliver substantial wattage, and tightly bundled cables in an enclosed tray get warm, which raises resistance and reduces effective distance.
• Cat6 or better is advisable for higher-power applications, as the thicker conductors handle current more comfortably.
• Check the switch's total power budget, not just its per-port capability. Twelve devices drawing thirty watts each exhaust most mid-range switches.

A Shopping List for a Small Office

1. Bulk Cat6 solid cable for permanent runs, pure copper, with the correct fire rating for each space.
2. Pre-made Cat6 stranded patch leads in assorted lengths. Buying these rather than making them saves time and produces more reliable terminations.
3. Keystone jacks and wall plates matching your chosen wiring standard.
4. A patch panel sized with spare capacity.
5. A punch-down tool for terminating solid cable.
6. A cable tester, at minimum a qualification tester rather than a simple continuity checker.
7. Cable management — trays, hook-and-loop ties, and labels. Not optional if you want to work on this again.

Installation Mistakes That Cause Later Failures

• Bending too tightly. Exceeding the minimum bend radius damages the internal geometry permanently.
• Over-tightening cable ties, which crushes the pairs and degrades performance invisibly.
• Running alongside power cables without separation, introducing interference.
• Untwisting too much at the termination. No more than about 13 millimetres should be untwisted at the connector.
• Pulling too hard, which stretches conductors.
• No labels, turning every future change into detective work.
• Leaving no spare capacity. Pull extra cables while the walls are open — the incremental cost is trivial and the future saving is enormous.

That final point is the most valuable advice here. The expensive part of cabling is the labour and the disruption, not the cable. Pulling four runs to each location instead of two costs a little more now and saves a small fortune the first time somebody needs an extra connection.