Why Cat6A when the switches are only gigabit

The question comes up on every fit-out. The switches are gigabit, the laptops are gigabit, Cat5e does gigabit, so why is the quote for Cat6A? The answer is that the cable is the only part of the network that will still be there in fifteen years, and it will be there because replacing it means opening the ceilings.

What is actually being bought

Structured cabling is the part of a network installation that is built into the building: the runs from the patch panel to every outlet, in the ceiling void, in the trunking, under the floor. Switches are swapped in an afternoon. Cabling is a refurbishment.

Cat6A carries 10 Gbps over the full 100 metres and, more relevant to most offices, it carries the higher PoE budgets — the ones that power a Wi-Fi 6E access point or a PTZ camera — with much less heat in a bundle. Cat5e does gigabit and low PoE, and that is the end of what it will ever do.

The access points are the reason today

Modern access points have multi-gigabit uplinks. A Wi-Fi 6 access point on a Cat5e run is a fast radio behind a slow cable, and the next generation of access points will not be specified with gigabit ports at all. The cable to the ceiling is the one that most needs headroom, and it is the one hardest to reach afterwards.

The cost difference is smaller than it sounds

The cable itself costs perhaps 40% more per metre. Labour is the same, and labour is most of the invoice. On a typical fifty-outlet office the difference between Cat5e and Cat6A is a few percent of the whole job, and a fraction of what it will cost to do the job twice.

Where Cat6 rather than Cat6A is fine

Short runs inside a room to desks that will only ever hold a laptop. Cat6 does 10 Gbps to 55 metres, which is most of a floor plate, and it is easier to terminate. What it does not do well is a dense bundle carrying high-power PoE — the heat builds up — so the runs to the ceiling are Cat6A regardless.

Things that matter more than the category

• Certification. Every run tested with a certifier to the standard, with the results handed over. An uncertified run is a run that might be fine.
• Labelling. Both ends, matching the patch panel, matching the plan. Unlabelled cabling is re-traced every time something moves, at an hourly rate.
• Spare outlets. Two per desk position and one in any wall that could hold a screen, a printer or an access point. Adding one later costs more than adding ten now.
• Separation from power. Data cable run alongside mains in the same trunking picks up interference, and the symptom is a link that works most of the time.

The honest summary

Cat6A is not for today's switches. It is for the switches that replace them, and the ones after that, on a cable nobody will want to touch again.