Cat5e vs Cat6 (and Cat6a): Ethernet Cable Categories Compared
Cat 5e and Cat 6 both carry gigabit Ethernet over the full 100 m. The real difference is 10 Gbps: Cat 6 manages it only on short runs (it should work up to 37 m, and up to 55 m if alien crosstalk allows), while Cat 6a carries it the whole 100 m. For CompTIA A+, Core 1 (220-1201) objective 3.2 covers copper cable categories, shielding, plenum ratings and the T568A and T568B wiring standards.
Ethernet cable categories compared
| Category | Bandwidth | Max speed | Max length | Standard |
|---|---|---|---|---|
| Cat 5 | 100 MHz | 100 Mbps | 100 m | TIA (superseded by Cat 5e) |
| Cat 5e | 100 MHz | 1 Gbps | 100 m | TIA; ISO Class D |
| Cat 6 | 250 MHz | 1 Gbps (10 Gbps on short runs: about 37 m, up to 55 m) | 100 m | TIA; ISO Class E |
| Cat 6a | 500 MHz | 10 Gbps | 100 m | TIA; ISO Class EA |
| Cat 7 | 600 MHz | 10 Gbps | 100 m | ISO Class F only (not a TIA category) |
| Cat 8 | 2000 MHz | 25 or 40 Gbps | 30 m | TIA; ISO Class I (Class II is ISO-only) |
Max length is the whole channel: up to 90 m of installed cable plus up to 10 m of patch cords. Cat 8's 30 m is a 24 m link plus 6 m of cords. Cat 5 is obsolete: TIA replaced it with Cat 5e, now the minimum for new data cabling. Gigabit Ethernet was designed to run on Cat 5, but only on installed Cat 5 that passes extra tests.
How far each category carries each speed
Cat 6's 10 Gbps figure comes from TIA's TSB-155 bulletin: it should work up to 37 m, may work to 55 m depending on alien crosstalk (interference between neighboring cables), and may need mitigation beyond that. Fluke Networks notes that TSB-155 is a guide for judging existing Cat 6, not a standard. If you need 10 Gbps on a new run, use Cat 6a.
Cat 5e vs Cat 6: what's actually different
- Bandwidth and crosstalk: Cat 6 is rated to 250 MHz against Cat 5e's 100 MHz, with tighter limits on crosstalk and signal loss. At 100 MHz, a Cat 6 channel must block about 10 dB more near-end crosstalk (NEXT) than Cat 5e: its minimum NEXT loss is 39.9 dB against 30.1 dB, so only about a tenth as much crosstalk gets through.
- Speed: both carry 1 Gbps and 2.5 Gbps over 100 m. Cat 6 also carries 5 Gbps over 100 m and 10 Gbps on short runs. Cat 5e isn't rated for 10 Gbps.
- Build: Cat 6 is usually thicker 23 AWG wire with a plastic spline separating the pairs; Cat 5e is usually 24 AWG with no spline. The standards set performance, not these details, so a cable's category rating is what counts.
For a home or small office on gigabit internet, Cat 5e is enough: the cable isn't the bottleneck. Cat 6 or Cat 6a makes sense for new runs that may need 2.5, 5 or 10 Gbps later.
Cat 6 vs Cat 6a, Cat 7 and Cat 8
- Cat 6a (augmented) doubles the bandwidth to 500 MHz and carries 10 Gbps over the full 100 m. TIA's current twisted-pair standard (ANSI/TIA-568.2-E, 2024) recommends Cat 6a or better for powering devices over Ethernet.
- Cat 7 isn't a TIA category. It's an ISO grade (Category 7 parts, Class F channel, 600 MHz) that must be fully shielded, and its standard connectors don't fit RJ45 ports; with RJ45 plugs it performs no better than Cat 6a. There's no Cat 6e standard either: it's a marketing name.
- Cat 8 is rated to 2000 MHz and carries 25 or 40 Gbps, but only over 30 m. It's shielded and built for short server-to-switch links in data centers.
Shielding, plenum and solid vs stranded
- UTP vs STP: unshielded twisted pair relies on the twists to cancel interference; shielded twisted pair adds foil or braid. Shielding helps where there's heavy electrical interference, such as factories and hospitals, and most offices don't need it. ISO names cables by their shields: U/UTP has none, F/UTP has an overall foil, and S/FTP has a braid plus foil around each pair.
- Plenum, riser and general purpose: cable run through a plenum, an air-handling space such as the space above a drop ceiling used for return air, must be plenum-rated (CMP): it resists flame spread and gives off little smoke. Riser cable (CMR) is for vertical runs between floors, and CM is for general use. A higher rating can always replace a lower one.
- Solid vs stranded: solid-conductor cable is for permanent runs in walls. Stranded cable bends more easily and is used for patch cords, but loses more signal: TIA allowed stranded cable 20% more attenuation.
Connectors and wiring: RJ45, T568A and T568B
Ethernet cable ends in an 8-pin RJ45 connector; the phone-line RJ11 is smaller. Each end is wired to T568B or T568A, which differ only by swapping the orange and green pairs. TIA lists T568A as preferred, but T568B is more widely used, and both perform the same. Wiring both ends the same way makes a straight-through cable. T568A on one end and T568B on the other makes a crossover cable, which ports with Auto-MDI-X don't need. The A+ cheat sheet has both pin orders.
Practise it: the free Wire Both Ends to T568B lab has you terminate a patch cable pin by pin.
What objective 3.2 covers
Core 1 (220-1201) objective 3.2 lists network cables: copper categories with the T568A and T568B standards, coaxial, shielded twisted pair (STP) including direct burial, unshielded twisted pair (UTP), plenum-rated cable, and single-mode and multimode optical fiber. Its connector list includes RJ45, RJ11, F-type and the punchdown block. It doesn't list the categories by number, so know the table above. Cable tools such as the crimper, cable tester and toner probe are in objective 2.8.
Then try the free Match the Cable to the Job PBQ, which has you pick the right cable for each install. More hands-on labs are on the A+ labs page.