Quick Answer: Twisted-pair copper stops at 328 ft (100 m) for 1000BASE-T, and that budget includes 33 ft (10 m) of patch cords, leaving 295 ft (90 m) of permanent link. Past the limit a link either refuses to train or trains and drops packets under load. Beyond 328 ft use fibre to a media converter or an SFP port; use a powered extender pair only where the far end has no local power. A mid-span switch is cheaper than fibre when the run is 400 to 600 ft (120 to 180 m) and power is available halfway.
The 100 m figure is a channel budget, not a cable specification, and it exists because attenuation, crosstalk and echo all grow with length at the same time. Reading the number as a suggestion produces links that pass a continuity test and fail a file copy, which is the most expensive kind of fault to diagnose on site.
Why the limit is 100 m
At 100 MHz, Cat 5e allows about 24 dB of insertion loss across the channel, and typical cable uses roughly 2 dB per 10 m at that frequency. The remaining budget covers crosstalk at both ends, return loss from impedance bumps, and the connectors. Beyond 328 ft the signal arriving at the receiver is too small relative to the echo of its own transmission.
Higher speeds shorten the budget rather than the cable. 10GBASE-T needs 500 MHz and 100 m of Cat 6a, or about 180 ft (55 m) of Cat 6. 2.5GBASE-T and 5GBASE-T each still allow 328 ft on the right cable, which makes them the cheapest way to gain speed on an existing run.
What failure looks like
Marginally over
A 400 ft (122 m) run often links at 1000 Mbit/s and works until the cable warms or a bundle is disturbed. Symptoms are CRC errors, TCP retransmits, and a throughput that falls from 940 Mbit/s to 300 Mbit/s under load. Ping stays clean because small packets fit the remaining margin.
Far over
At 600 ft (183 m) the PHY usually falls back to 100 Mbit/s or refuses to link at all, and the port light stays dark. That is a cleaner fault: the hardware is telling you the channel is outside specification, and no amount of driver tuning will change it.
Four ways past the limit
Fibre is the only option that removes the distance problem instead of working around it. A duplex OM3 run with 10GBASE-SR reaches 984 ft (300 m) and OM4 reaches 1,312 ft (400 m), at under 0.5 ms of added latency. The cost sits in the transceivers at each end, and single-mode parts reach 6 miles (10 km) for a modest premium.
A powered extender pair converts to a proprietary scheme and back, giving 100 Mbit/s over 1,600 ft (490 m) on ordinary copper, or 1 Gbit/s over about 330 ft (100 m) of additional distance. Latency is under 2 ms and the far unit can usually be powered over the same pair, which suits a camera on a pole. It will not pass 10GBASE-T.
A mid-span switch at 250 ft (76 m) and again at 500 ft (150 m) keeps every segment inside the limit and adds a managed hop. Use an unshielded ethernet cable for the interior segments and earth nothing, because a floating shield on a long run acts as an aerial for common-mode noise. Dress the rack ends with a short ethernet jumper cable so the horizontal run is never flexed at a panel.
Comparing the four options
| Method | Max reach | Throughput | Latency added | Power at far end |
|---|
| Cat 6 copper | 328 ft (100 m) | 1 Gbit/s | None | PoE, 90 W |
| Cat 6a copper | 328 ft (100 m) | 10 Gbit/s | None | PoE, 90 W |
| Fibre, OM3 duplex | 984 ft (300 m) | 10 Gbit/s | Under 0.5 ms | Local only |
| Extender pair | 1,600 ft (490 m) | 100 Mbit/s | Under 2 ms | Over the pair |
| Mid-span switch | 328 ft per hop | 1 Gbit/s | About 0.1 ms | Mains socket |
Practical scenarios
- Situation: A 420 ft (128 m) run to a gatehouse that links at gigabit but stalls on file copies. Convert to fibre rather than adding an extender that caps the link at 100 Mbit/s.
- Situation: A camera 700 ft (213 m) down a yard with no power at the far end. Use an extender pair powered from the head end and accept 100 Mbit/s, which is ample for 4K video at 12 Mbit/s.
- Situation: A 560 ft (170 m) workshop span with a socket at the halfway wall. Fit a mid-span switch and two 280 ft segments; the cost is a switch, not a fibre run.
- Situation: A temporary 350 ft (107 m) link for an event. Use a flex ethernet cable rated for re-coiling and keep it out of walkways, then replace it with permanent fibre.
FAQ
Can I just add a coupler and a second lead?
Only inside the 328 ft budget. Two 200 ft leads joined by a coupler exceed the channel limit and add a reflection point. Use a single lead of the right length, or move to fibre.
Does a switch count as a repeater?
A switch terminates the link and starts a new one, so each segment gets its own 328 ft. A hub or a passive repeater does not, which is why they are no longer sold for this purpose.
Is shielded cable better on long runs?
Only when it is bonded to earth at both ends and the building has a low-impedance path. An unbonded shield on a 300 ft run collects noise and makes crosstalk worse rather than better.
