Ethernet Standards (IEEE 802.3)
Common Ethernet physical layer standards.
IEEE 802.3 defines the physical layers of Ethernet. Each standard pairs a speed with a media type and a distance limit, and choosing the right one for a link is a matter of matching cable plant to requirement: twisted pair for structured copper cabling, multimode fiber for short reaches inside a building, and single-mode fiber for longer spans.
This table covers the standards you will encounter most: 1000BASE-T, 10GBASE-T, the SR and LR fiber variants of 10G, 25G, 40G, 100G, and the first 400G standards.
An Ethernet port is the socket the cable plugs into, and the standard behind the port sets the ceiling on speed and reach. For copper runs the cable category matters as much as the port: Cat5e carries 1G and 2.5G to 100 metres, Cat6 reaches 10G up to about 55 metres, and Cat6a carries 10G over the full 100 metres.
| Standard | Name | Speed | Media | Distance |
|---|---|---|---|---|
| 802.3ab | 1000BASE-T | 1 Gbps | Cat5e+ | 100 m |
| 802.3an | 10GBASE-T | 10 Gbps | Cat6a+ | 100 m |
| 802.3ae | 10GBASE-SR | 10 Gbps | OM3/OM4 MMF | 300/400 m |
| 802.3ae | 10GBASE-LR | 10 Gbps | OS2 SMF | 10 km |
| 802.3by | 25GBASE-SR | 25 Gbps | OM4 MMF | 100 m |
| 802.3ba | 40GBASE-SR4 | 40 Gbps | OM3/OM4 MMF | 100/150 m |
| 802.3bj | 100GBASE-SR4 | 100 Gbps | OM4 MMF | 100 m |
| 802.3cu | 100GBASE-FR1 | 100 Gbps | OS2 SMF | 2 km |
| 802.3bs | 400GBASE-SR16 | 400 Gbps | OM4 MMF | 100 m |
| 802.3ck | 100GBASE-CR1 | 100 Gbps | Copper DAC | 2 m |
Frequently Asked Questions
What is an Ethernet port?
An Ethernet port is the physical socket on a device where a network cable connects. On copper links it is an RJ45 jack wired for 8P8C connectors, and it negotiates a speed such as 100 Mbps, 1 Gbps, or 10 Gbps. On fiber links the port is a cage that accepts a transceiver module instead of a fixed jack.
What is the difference between Ethernet and a LAN?
Ethernet is the link layer technology that carries frames across a cable, while a LAN is the local network those cables and devices form. A LAN can run over Ethernet, Wi-Fi, or both, and Ethernet is simply the wired option.
What cable do I need for 1G, 2.5G, and 10G Ethernet?
Cat5e handles 1G and 2.5G up to 100 metres. Cat6 reaches 10G to roughly 55 metres and 2.5G or 5G to 100 metres. Cat6a carries 10G over the full 100 metres, which is why it is the usual choice for new 10G copper runs.
What is the maximum cable length for Ethernet?
100 metres (328 feet) for twisted pair, split into 90 metres of permanent horizontal cabling and 10 metres of patch cords. Fiber reaches much further: multimode carries 10G to about 400 metres and single-mode to 10 kilometres or more.
What does 1000BASE-T mean?
The name encodes the standard: 1000 is the speed in megabits per second, BASE means baseband signaling, and T means twisted pair copper. So 1000BASE-T is 1 Gbps Ethernet over copper cable, and 10GBASE-SR is 10 Gbps over short-reach multimode fiber.
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