Quick Answer: 20 ft is 6.1 m, about one-fifth of the 328 ft (100 m) channel limit, so distance is not the constraint. Conductor type is. Buy a 24 AWG stranded patch lead for anything that gets plugged and unplugged, 23 AWG solid core for a run that stays put, and never 28 AWG flat cable for 30 W of PoE. Cat 5e at 100 MHz carries gigabit at this length; Cat 6a buys 10GBASE-T headroom and better alien crosstalk margin.
At six metres the electrical budget is generous and the mechanical budget is not. A lead that is flexed twice a day fails at the plug long before the copper runs out of bandwidth, and a solid core lead bent to a 10 mm radius will pass a continuity test and fail on insertion loss.
Length is the easy part
A 1000BASE-T channel allows 328 ft (100 m) of which 33 ft (10 m) may be patch cords, so a single 20 ft lead uses a fifth of the allowance and leaves 295 ft (90 m) for the permanent link. Insertion loss at 6 m is roughly 3 to 4 dB against a limit near 24 dB at 100 MHz, which is why almost any decent lead works electrically.
That headroom disappears under PoE. A 30 W port pushes about 0.6 A through two pairs, and the resulting temperature rise in a bundled cable adds loss that the datasheet figures do not include. Twenty feet of 28 AWG in a tight bundle is where that shows.
Stranded or solid
Stranded patch leads
Seven strands of 32 AWG make a 24 AWG conductor that survives thousands of flex cycles. That flexibility costs about 20 percent more attenuation than solid, which is irrelevant at 6 m and relevant at 90 m. Use stranded for desk leads, rack jumpers and anything a user will handle.
Solid core runs
One 23 AWG conductor has lower loss and lower cost per metre, but it work-hardens and cracks if flexed repeatedly. Terminate it on a jack with a punch-down tool and treat it as fixed infrastructure. A solid lead used as a daily patch will fail inside a year, usually at the plug boot.
Twenty feet in five builds
| Lead | Conductor | PoE at 30 W | Bend radius | Use |
|---|
| Cat 5e stranded | 24 AWG | Fine | 25 mm | Desk patch |
| Cat 6 stranded | 24 AWG | Fine | 30 mm | Rack jumper |
| Cat 6 solid | 23 AWG | Fine | 4x diameter | Fixed run |
| Cat 6a shielded | 23 AWG | Fine | 4x diameter | 10GBASE-T run |
| Slim flat | 28-30 AWG | Derate, 15 C rise | 15 mm | Short desk lead |
What the jacket has to survive
Indoors, a CM or CMR jacket satisfies most installations, and CMR is required in a riser between floors. A plenum ceiling needs CMP, which is a different compound and a different price. Outdoors, or in a wet wall, the jacket must be UV-stabilised and the assembly gel-filled; an ordinary PVC lead will absorb water along the braid within a season and the link will train at 100 Mbit/s or drop entirely.
If the run leaves the building envelope, order an ethernet cable weatherproof assembly and keep the connector under a drip loop. For a run that has to last ten years at 10GBASE-T, choose a cat6a cable in solid 23 AWG and earth the shield at one end only.
The vocabulary trips people up more than the physics does. If the question is whether the lead in the drawer will work, the answer is yes: is lan cable same as ethernet explains why the two terms describe the same 8P8C assembly in most buildings.
Practical scenarios
- Situation: A meeting room table with a 20 ft lead to a floor box. Use 24 AWG stranded Cat 6 and add a 6 in (150 mm) service loop so the plug is never under tension.
- Situation: A ceiling access point drawing 30 W of PoE. Run 23 AWG solid Cat 6a and keep the bundle to four cables or fewer to limit the temperature rise.
- Situation: A laptop user who re-plugs twice a day. Retire the 30 AWG flat lead; the conductor breaks at the boot after roughly 1,500 cycles.
- Situation: A camera 20 ft outside a wall. Use a UV-rated gel-filled assembly, drip loop at the entry point, and a shielded jack bonded to earth.
FAQ
Will 20 ft give full gigabit speed?
Yes, on any Cat 5e or better lead with all four pairs terminated. Length contributes 3 to 4 dB of loss against a 24 dB budget at 100 MHz, so the lead is not the limiting factor.
Can I join two 20 ft leads with a coupler?
You can, and the channel still passes at 40 ft, but each coupler adds a discontinuity and a failure point. Use it for a temporary link and replace it with a single lead before the install is signed off.
Does Cat 6a help at this length?
Only for 10GBASE-T or for noisy routes beside mains and motors. At 6 m, Cat 5e already passes 1000BASE-T with margin, so the extra cost buys future headroom rather than present performance.
