An Ethernet switch is a networking device used to connect multiple wired devices like computers, printers, IP cameras, and servers in a Local Area Network (LAN). It has multiple RJ45 ports, and each device connects to the switch using an Ethernet cable.

Unlike a simple hub that broadcasts data to all ports, a switch is intelligent; it sends data only to the specific device that needs it, which improves speed, reduces collisions, and makes the network more efficient.

How Does an Ethernet Switch Work?

When a device sends data over the network, the data is broken into frames and forwarded to the switch. The switch reads the header of each frame and checks the MAC address (a unique hardware address) of the source and destination device.

The switch maintains an internal MAC address table, which maps MAC addresses to the physical ports. If the destination MAC is known, the switch forwards the frame only to that specific port; if it is unknown, the switch temporarily sends it out to all ports and learns the correct path when the destination responds.

Main Functions of an Ethernet Switch

  • Learning: The switch learns which device is connected to which port by reading the source MAC address of incoming frames and storing it in its table.
  • Forwarding and Filtering: It forwards frames only to the correct destination port and filters out unnecessary traffic from other ports.
  • Collision Reduction: Each port on a switch is its own collision domain, which reduces collisions and improves performance compared to hubs.
  • Full-Duplex Communication: Most modern switches support full-duplex, allowing devices to send and receive data at the same time.

Types of Ethernet Switches

  • Unmanaged Switch: Plug-and-play device with no configuration, commonly used in small offices or homes.
  • Managed Switch: Allows configuration of VLANs, QoS, port security, monitoring, etc., used in enterprise and industrial networks.
  • PoE Switch (Power over Ethernet): Provides both data and power over the same Ethernet cable to devices like IP cameras, VoIP phones, and Wi-Fi access points.

Where Is an Ethernet Switch Used?

  • Office networks to connect PCs, printers, and servers.
  • Industrial control systems to connect PLCs, HMIs, SCADA, and field devices.
  • CCTV/IP camera networks for video surveillance.
  • Home networks for smart TVs, gaming consoles, and NAS devices.