Ethernet standards from 10 Mbit/s to 400 Gbit/s
Ethernet is defined by the IEEE 802.3 family, and each physical-layer (PHY) standard pairs a speed with a specific medium and reach. This reference lists the common copper and fibre standards — from legacy 10BASE-T to modern 400GbE — with the IEEE designation, maximum speed, required cable, and maximum distance.
Decoding the standard name
Each Ethernet standard name encodes three things. The leading number is the speed (10, 100, 1000 Mbit/s, or in Gbit/s for 10G and up). BASE means baseband signalling — the whole cable carries one Ethernet signal. The suffix names the medium: -T is twisted-pair copper, -SX/-SR is short-reach multimode fibre, -LX/-LR is long-reach single-mode fibre, and a trailing digit (SR4, LR4) gives the number of parallel lanes or wavelengths.
Some examples decoded:
| Standard | Speed | Medium | Meaning of suffix |
|---|---|---|---|
| 100BASE-TX | 100 Mbit/s | Cat5e copper | T=twisted pair, X=4B5B encoding |
| 1000BASE-T | 1 Gbit/s | Cat5e copper | T=twisted pair |
| 10GBASE-SR | 10 Gbit/s | Multimode fibre | SR=short reach |
| 10GBASE-LR | 10 Gbit/s | Single-mode fibre | LR=long reach (~10 km) |
| 100GBASE-SR4 | 100 Gbit/s | Multimode fibre | SR=short reach, 4=four lanes |
| 2.5GBASE-T | 2.5 Gbit/s | Cat5e or Cat6 copper | NBASE-T standard |
Copper cabling: which category for which speed
Copper BASE-T standards run over twisted-pair cable, and the cable category determines the maximum speed and distance:
- Cat5e: up to 1000BASE-T (Gigabit) at 100 m, and up to 2.5GBASE-T at 100 m. Cat5e is the minimum for any modern installation.
- Cat6: up to 5GBASE-T at 100 m and 10GBASE-T at reduced distance (37–55 m depending on the channel). Cat6 is suitable for most office installations being deployed today.
- Cat6A: up to 10GBASE-T at the full 100 m. Cat6A has thicker sheathing and tighter shielding than Cat6, making it bulkier but necessary for full 10G copper runs.
- Cat7 and Cat8: Cat7 is 10G at 100 m (similar to Cat6A), while Cat8 supports 25GBASE-T or 40GBASE-T over short runs (30 m), designed for data centre top-of-rack connections.
Fibre: SR versus LR and the role of the transceiver
Fibre Ethernet separates the standard (IEEE) from the optic (transceiver form factor). The same switch port with an SFP+ cage can run:
- An SR optic (850 nm laser, multimode fibre, up to a few hundred metres) for connections within a building or campus
- An LR optic (1310 nm laser, single-mode fibre, up to 10 km) for building-to-building or metro connections
- A CWDM4 or PSM4 optic for 100G over single-mode at 2 km
Because transceivers are field-replaceable, network operators can extend an existing fibre run’s reach just by swapping the optic — without changing the switch port or the cable.
Tips and notes
- Auto-negotiation lets two ports agree on the fastest common speed and duplex. Mismatched manual speed settings are a classic cause of slow or unstable links; always let ports negotiate unless you have a specific reason to force a setting.
- 2.5GBASE-T and 5GBASE-T (NBASE-T, IEEE 802.3bz) let existing Cat5e and Cat6 infrastructure carry 2.5 or 5 Gbit/s without rewiring. They are the dominant choice for Wi-Fi 6/6E access-point uplinks where the AP’s radio exceeds 1 Gbit/s aggregate throughput.
- Distances are maximums for a clean channel. Connectors, patch panels, and total link length all reduce real-world reach. Cable testing with a certified tester is essential before commissioning 10G or above on copper.