UK How an Ethernet switch works
An Ethernet switch is the device that joins the wired devices on a local network together. Each port is its own link to one device, or to another switch, and the switch decides where every piece of traffic goes.
Ethernet traffic travels in frames, and every frame carries the MAC address of the device that sent it and the device it is meant for. When a frame arrives, the switch records the sender’s address against the port it came in on, building a MAC address table. It then looks up the destination address and sends the frame out of that port alone. If the destination is not in the table yet, the switch floods the frame to every port once, and the reply teaches it where that device lives.
Because each port is a separate link running in full duplex, devices can send and receive at the same time without colliding. That is the big change from the older network hub, which repeated every frame to every port so that all devices shared one slow, collision-prone link.
What an Ethernet switch does on a network
A switch connects devices that belong to the same local network. It does not connect that network to the internet or to other sites; that is the job of a router, which works at Layer 3 with IP addresses. Our guide to what a router does covers that side. In a typical installation, the switch links the computers, cameras, PLCs and access points in a cabinet or building, and one switch port connects up to the router.
A switch also sets the speed of each link. A port negotiates the fastest rate both ends support, so a 1 Gbit/s camera and a 10 Gbit/s server can share the same switch. Uplink ports, often SFP or SFP+ slots, carry the combined traffic to the next switch or to the core of the network.
Types of Ethernet switch
Switches are grouped by how much control they give you, whether they supply power, and where they are built to run.
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Unmanaged switches. Plug-and-play switching with no configuration. Unmanaged industrial switches suit small, flat networks where every device can see every other device.
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Managed switches. Add VLANs, traffic priority (QoS), redundancy protocols such as RSTP, and monitoring through a web page, command line or SNMP.
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PoE switches. Also supply DC power to cameras, access points and sensors over the same Ethernet cable, within a total power budget.
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Layer 3 switches. Managed switches that also route traffic between VLANs and subnets in hardware, inside a site.
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Industrial and embedded switches. Fanless, wide-temperature switches for DIN rail, panel or vehicle mounting, and board-level switches that fit inside another system.
Switch speeds and port types
Ethernet speeds are set by the IEEE 802.3 standards. Most switches mix copper RJ45 ports for devices with faster fibre or copper uplinks.
| Speed | Common name | Typical copper standard | Typical use on a switch |
|---|---|---|---|
| 100 Mbit/s | Fast Ethernet | 100BASE-TX | Legacy PLCs, meters and serial gateways |
| 1 Gbit/s | Gigabit Ethernet | 1000BASE-T | Most device ports today |
| 2.5 and 5 Gbit/s | Multi-gigabit | 2.5GBASE-T, 5GBASE-T | Wi-Fi 6 and 7 access points, faster edge devices |
| 10 Gbit/s | 10GbE | 10GBASE-T or SFP+ | Uplinks, servers and multi-camera systems |
| 25 Gbit/s and above | 25GbE and faster | SFP28 and larger modules | Core and data-centre links |
Copper Ethernet reaches around 100 m per run. For longer links between cabinets or buildings, a fibre module in an SFP slot takes over, and the module type sets the reach.
What makes an industrial Ethernet switch different
Office switches are built for air-conditioned rooms and mains power. On a factory floor, in a roadside cabinet or on a vehicle, the switch has to cope with heat, vibration, electrical noise and DC supplies. Our guide to choosing managed or unmanaged industrial switches walks through the selection, and the main differences are below.
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Fanless, sealed construction. Metal housings cooled by conduction, with no fan to clog with dust, and wide operating temperatures, often −40 to 75 °C.
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DIN rail and panel mounting. Built to clip into a control cabinet next to PLCs and power supplies.
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Redundant DC power inputs. Two supplies, typically 12 to 48 V DC, so one can fail without taking the network down.
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Ring redundancy. Managed models recover from a broken cable in a ring topology, often in milliseconds rather than the seconds standard protocols take.
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Locking connectors. M12 connectors on rugged Ethernet switches resist vibration on trains, vehicles and machines.
Quick answers on Ethernet switches
Ethernet switches: common questions
Does an Ethernet switch reduce speed?
No. Each port runs at its full negotiated speed, and a non-blocking switch can carry every port at once. Devices only slow down if many of them share one uplink that is slower than their combined traffic.
Is a network switch the same as an Ethernet switch?
Usually, yes. Almost all network switches today are Ethernet switches. The term network switch is broader and can also cover other technologies, such as InfiniBand or Fibre Channel switches in data centres.
How many devices can I connect to an Ethernet switch?
One per port. An 8-port switch takes eight links. To add more, connect switches together; the MAC address table in a typical switch holds thousands of entries, so the port count is the practical limit.
Can you connect two Ethernet switches together?
Yes. Link a port on one to a port on the other, ideally a faster uplink. Avoid loops unless the switches are managed and run a redundancy protocol, because a loop between unmanaged switches floods the network.
Can wireless devices use an Ethernet switch?
Through an access point. Phones and laptops connect to a wireless access point, and the access point connects to a switch port, often powered by PoE.
We supply industrial, rugged and embedded Ethernet switches from our partners, and specify the port count, speeds, power inputs and redundancy to suit your network and installation.