Ethernet Switch Definition

What is an Ethernet Switch?

An Ethernet switch is a networking device that is found inside an organization’s local area network (LAN). It connects multiple devices to a particular subnet.

One defining attribute of a switch is that it primarily operates at the Data Link layer of the OSI model. Instead of using IP addresses for routing traffic, an Ethernet switch uses hardware MAC addresses.

How Does an Ethernet Switch Work?

Ethernet switches are networking devices that work inside of a LAN. Unlike a router, they can’t be used to define the boundary between a private network and the public Internet.

One of the main reasons for this is that Ethernet switches mainly operate at Layer 2 of the OSI model, which is the Data Link Layer. At this layer, addressing is performed using hardware MAC addresses rather than IP addresses.

A network interface card (NIC) in a computer will have its own MAC address associated with it. Ethernet switches have multiple ports and will maintain a lookup table that maps a port to the associated MAC address. This mapping enables the switch to send traffic to the appropriate device based on its MAC address.

A switch’s main purpose is to perform MAC address-based routing of traffic. However, Ethernet switches can also provide more advanced features. For example, a switch may operate at multiple levels of the OSI model, support virtual LANs (VLANs), or have built-in Quality of Service (QoS) functionality.

Switch vs. Hub vs. Router

Switches are one of a few different devices that can route traffic within a network, and, in some situations, these devices might be interchangeable. The main differences between switches and similar devices include:

• Hub: Switches and hubs are both devices designed to work inside a corporate LAN and have multiple ports to which devices can be connected. However, a hub will broadcast every packet on every port (which is bad for efficiency and security), while a switch uses MAC addresses to send packets only to the intended recipient.
• Router: Routers are typically used to define LAN boundaries and route traffic between LANs, unlike switches that work inside of a LAN. Routers mainly operate at Layer 3 of the OSI model and use IP addresses for routing, while switches work at Layer 2 and rely on MAC addresses.

In general, hubs are obsolete due to their numerous limitations, which is why most internal networks will be built using switches. In some cases, such as a home network or predominantly wireless network, a router may be the only thing used since only a few ports are needed.

Conclusion

An Ethernet switch is a network device used within a LAN. It mainly operates at Layer 2 of the OSI model and uses MAC addresses to route traffic to its destination (unlike a router). It differs from a hub mainly because switches will send packets to a single port (based on MAC address), while hubs will broadcast all received traffic to all connected devices (which is bad for security).