Ethernet Cat Standards Explained: Cat 5, 5e, 6 & 6a (A+)

Ethernet Cable Categories: Cat 5 Through Cat 6a

Oct 9, 2026 · @Ken

The table below is the whole story in one glance, and this write-up fills in the reasoning behind it — why each cable category tops out at the speed and distance it does, what changes physically between one category and the next, and where this fits inside the broader A+ exam.

Why Cable Category Matters

Every one of these cables is the same basic idea: four twisted pairs of copper wire, terminated in an eight-position connector. What actually changes from Cat 5 to Cat 6a is manufacturing precision — tighter, more consistent twists per pair, better-controlled impedance, and thicker conductors that all work together to cut down on crosstalk, the interference one pair induces in its neighbors. Twisting the pairs is what cancels out that interference in the first place, and the tighter and more uniform the twist, the higher the frequency — and therefore the data rate — the cable can carry cleanly before errors start creeping in. A category rating isn't a marketing label; it's a certified guarantee that a cable meets a specific electrical performance standard at a specific frequency.

Reading the Cat Standards Table

Cat 5 is the oldest standard still worth knowing, rated for 100 Mbps over the standard 100-meter run using 100BASE-TX, better known as Fast Ethernet. It's largely obsolete for new installations today, but it still shows up in older buildings and on the exam.

Cat 5e — the "e" stands for enhanced — tightened the manufacturing tolerances enough to push the same 100-meter run up to a full 1 Gbps over 1000BASE-T, Gigabit Ethernet. For years this was the default cable pulled in new structured cabling jobs, and it's still extremely common in the field.

Cat 6 is where the table gets interesting, because it has two ratings instead of one. At the standard 100-meter distance, Cat 6 is only guaranteed for the same 1 Gbps as Cat 5e over 1000BASE-T — the improvement is headroom and lower error rates, not raw speed. Push it to 10GBASE-T, 10 Gbps Ethernet, and the maximum guaranteed distance drops sharply to 55 meters. That's not a typo or a marketing asterisk; it's a direct consequence of how much faster 10GBASE-T signaling is, which makes the cable far more sensitive to crosstalk and attenuation the farther the signal travels. Past 55 meters at that speed, Cat 6 can no longer guarantee a clean enough signal.

Cat 6a — augmented Cat 6 — is the fix for that gap. Tighter construction and better shielding against crosstalk let it hold the full 10 Gbps over 10GBASE-T all the way out to the standard 100-meter run, which is exactly why it's become the practical minimum for new installations expected to support 10-gigabit links.

UTP vs. STP

Every cable in the table above is typically unshielded twisted pair (UTP) — the twisting alone handles crosstalk, with no extra shielding layer, which keeps the cable thinner, cheaper, and easier to pull through conduit. Shielded twisted pair (STP) adds a foil or braided shield around the pairs — sometimes around the whole bundle, sometimes around each individual pair — to block external electromagnetic interference. STP is worth the added cost and stiffness in environments with heavy electrical interference nearby, like next to fluorescent ballasts, large motors, or industrial equipment, where UTP alone can't keep the signal clean no matter how tight the twist is.

Connectors and Wiring Standards

None of this matters without a properly terminated connector on each end, almost always an RJ45 plug wired to either the T568A or T568B standard. The crimping process, the pinout differences between those two standards, and how they combine to make a straight-through versus a crossover cable are their own topic — the RJ45 / RJ11 Cable Crimper article covers that ground in detail. For runs terminated at a patch panel instead of crimped directly, a punchdown tool seats the same conductors into an insulation-displacement connector rather than a modular plug, and either termination method should be checked afterward with a cable tester or certifier to confirm the run actually performs at its rated category.

Plenum vs. PVC Jacketing

Category rating describes electrical performance, but the cable's outer jacket is a separate, equally exam-relevant spec: what happens if it burns. Ordinary cable is jacketed in PVC, which is fine for most runs but releases thick, toxic smoke when it burns. Any cable routed through a plenum space — the area above a drop ceiling or under a raised floor that a building's HVAC system uses to circulate air — has to carry a plenum-rated jacket instead, made from a fire-retardant compound that burns slower and releases far less toxic smoke, specifically because that airspace would otherwise pump smoke straight through the rest of the building. Pulling PVC-jacketed cable through a plenum space isn't just bad practice, it's a fire code violation in most jurisdictions, which is exactly why CompTIA tests the distinction alongside the category ratings themselves.

Why Copper Still Matters Next to Fiber

Fiber optic cable outperforms every category in this table on raw bandwidth and distance, but copper twisted pair hasn't gone anywhere, for a simple reason: cost and power. A UTP or STP run is far cheaper to buy, terminate, and troubleshoot than fiber, and critically, copper is what carries Power over Ethernet — a device like a wireless access point or a VoIP phone can't get electricity over a glass fiber strand. That's why most horizontal cabling to a desk or an access point is still Cat 6 or Cat 6a copper, while fiber takes over for backbone and long-haul runs between switches and buildings.

Exam Tips: Where This Fits in 220-1101

Cable categories sit under objective 3.1, "Explain basic cable types and their connectors, features, and purposes," part of Domain 3.0, Hardware — 25% of the exam, the single largest domain on Core 1. That same objective is broad: alongside Cat 5, Cat 5e, Cat 6, and Cat 6a, it also covers unshielded and shielded twisted pair, coaxial and fiber cable, peripheral cables like USB and Thunderbolt, video cables, and connector types from RJ45 to ST, SC, and LC fiber connectors. The category ratings in the table above are the piece of that objective this post focuses on.

A few things worth locking in before test day:

• Know Cat 6's split rating cold. 1 Gbps at 100 meters, but only 10 Gbps at 55 meters — that distance drop at higher speed is a favorite exam detail.
• Cat 6a is the one with no asterisk. It's the only category in this table that holds 10 Gbps at the full 100-meter standard distance.
• UTP vs. STP is about interference, not speed. Shielding is added to fight electromagnetic interference, not to increase the category's maximum data rate.

Quick Reference

Category	Max Speed	Max Distance	Ethernet Standard
Cat 5	100 Mbps	100 m (328 ft)	100BASE-TX
Cat 5e	1 Gbps	100 m (328 ft)	1000BASE-T
Cat 6	1 Gbps / 10 Gbps	100 m / 55 m	1000BASE-T / 10GBASE-T
Cat 6a	10 Gbps	100 m (328 ft)	10GBASE-T

You don't need to memorize a cable manufacturer's spec sheet. Know the four categories in order, know that Cat 6 is the one with two different distance ratings depending on speed, and know that shielding in STP addresses interference, not throughput.

Source

CompTIA A+ Core 1 (220-1101) Exam Objectives — Objective 3.1 (Domain 3.0, Hardware)