What Is an Ethernet Switch?

An Ethernet switch is a type of network hardware that is foundational to networking and the internet. Ethernet switches connect cabled devices, like computers, Wi-Fi access points, PoE lighting and IoT devices, and servers, in an Ethernet LAN so they can communicate with each other and to the internet.

View Cisco Catalyst 9000 portfolio

What is Ethernet?

Ethernet technology is designed to solve the problem of packet collision in a shared network by having network-connected devices follow a set of rules that allow devices to talk to each another without talking over each other. These network-connected devices are physically connected with a cable to an Ethernet switch that then manages the flow of data between devices, applications, data, cloud services and the internet.

More formally, Ethernet is a common name for the IEEE 802.3 standard based on the Carrier Sense Multiple Access/Collision Detection (CSMA/CD) protocol, which defines when to transmit and what is to happen if a collision is detected, as well as endpoint addressing, transmission speeds, and media. The IEEE 802.3 media standards focus on cable type (coaxial, twisted-pair and fiber), bandwidth capacity (10 Mbps to Tbps) and transmission distance.

Ethernet has evolved dramatically since its first application and today is the de facto protocol for IP-based networks and the internet. Ethernet switches have also become the common network switch type and foundational technology for most networks.

How is Ethernet different from Wi-Fi?

Wi-Fi can be seen as an extension to an Ethernet access network allowing wireless connections to an Ethernet network. Wi-Fi allows the freedom of mobility without the need to connect with a network cable.

From a network point of view, typically Wi-Fi requires a wireless access point device to act as the interface to the network. The end device is connected to the access point and the access point is connected to, or is part of, the Ethernet switch instead of being connected directly to the switch by physical cable.

Wi-Fi and Ethernet are outlined by separately in the IEEE 802 protocols, with Ethernet defined by IEEE 802.3 and Wi-Fi defined by 802.11.

How do Ethernet connections differ from Wi-Fi?

From a user perspective, an access Ethernet connection requires a physical cable and provides a dedicated link from the switch to the end device with bandwidth up to the speed of the connected port. Wi-Fi connections are wireless and allow devices to be located anywhere that can receive a Wi-Fi signal but share the bandwidth of the connecting Wi-Fi access point with other devices connected to the same AP.

Are an Ethernet switch and hub the same?

No. While they are both examples of data network hardware, a hub is a Layer 1 device, which is part of the physical transport layer and acts as a broadcast/aggregator but does not manage any of the traffic.

An Ethernet switch manages the flow of data, directing data it receives in one port to another port based on information in a data packet's header, namely the sending and receiving MAC addresses. The switching process significantly improves the efficiency of the network as opposed to a hub.

Can Ethernet switches act as routers?

Yes. Most modern Ethernet switches are capable of handling both types of data-forwarding tasks in a network environment. However, by design, routers are better suited to managing a high volume of data traffic quickly and efficiently.

What is Power over Ethernet (PoE)?

PoE refers to the ability to provide low-voltage (<100W), DC electrical power to network devices via the same, twisted-pair copper Ethernet cables used to transmit data. This eliminates the need for a separate AC power source, allowing for more flexible placement options without concern for proximity to a power outlet or the need to implement an AC electrical infrastructure. Examples of devices that use PoE include LED lighting, window shades, monitors, sensors, wireless access points, and voice over IP (VoIP) phones.

PoE is a simple technology, and it's not new. It's a low-cost, reliable, and flexible approach to powering smart devices in a network and is crucial to enabling smart buildings and their ecosystems of network-connected devices such as window shades, lighting, thermostats, and security systems.

What are IEEE 802.3af, IEEE 802.3at, and IEEE 802.3bt standards?

As part of the IEEE 802.3 standards that define Ethernet, the 802.3af, 802.3at, and 802.3bt standards define common techniques used to transmit power over copper Ethernet cables (PoE).

The IEEE PoE standards have significantly evolved since the initial IEEE 802.3af standard that defined up to 15.4W of DC power. This was later superseded by the IEEE 802.3at standard, increasing power up to 25.5 W.

The latest standard, IEEE 802.3bt, was published in 2019 and allows for significantly more power. Currently, up to 100W of power is available to deliver high-speed connectivity over LAN connections and enable many new applications.

How do Ethernet switches work?

Ethernet switches connect multiple devices together by physically cabling those devices to the same switch or devices connected to another switch that is connected the same network.These cables include coaxial, fiber, and Ethernet cable twisted-pair.

Once a device is connected to a port, the Ethernet switch manages the flow of data between the device and other devices, applications, data, cloud services, and the internet. The switching process directs incoming and outgoing data to the correct port on the switch based on the port of the sending device and the sending and destination MAC addresses. The MAC address of both sender and destination are included, with the data being sent in an Ethernet frame.

Every Ethernet compatible device has a hardcoded physical address called a MAC address that the connecting switch uses to uniquely identify a device.

When a switch receives an Ethernet packet, it stores the sending device's MAC address and the port it is connected to in a locally held table called a MAC address table. The switch process then checks the MAC address table to see if the destination MAC address is connected to the same switch. If it is, the switch forwards the packet to the known destination port. If not, the switch broadcasts the packet to all ports and waits for a response.

If the switch is connected directly to the destination device, the device accepts the data packet, responds, and the transmission is complete. If the device is connected to another switch, the next switch will repeat the lookup and forward process until the frame reaches the intended destination.

Ethernet switches vary dramatically in scale and capabilities, from the very small like those in a home, to the very fast terabit speed core switches. There are different types of Ethernet switches to handle different sizes or structures of networks: access, distribution, and core. Switching networks often have a tree-root structure, with smaller switches connected to devices at the access edge and larger switches acting as distribution, then larger acting as core switches.

Modernizing Ethernet switches

Why should Ethernet switches be updated?

Since their introduction in 1990, Ethernet switches have been essential to enabling network connectivity. But they've taken on new importance in the modern digital era because of their critical role in making wired and wireless connectivity possible and supporting the growing Internet of Things (IoT).

Ethernet switches are also foundational to creating smart buildings, where the network is the fourth utility after electric, water, and gas.

Many Ethernet switches are now designed as PoE switches. Now that PoE can deliver up to 100W of power, it can support network-connected devices that need more power to run, such as medical devices, large monitors, PTZ cameras, and industrial lighting. The latest PoE advancements open the door to highly connected and efficient smart work and living environments.

Today, many Ethernet switches feature software, or they can connect with software that takes in and analyzes data that the switch collects. By applying artificial intelligence (AI) and machine learning (ML), that data can be turned into actionable data and used to optimize smart environments.

Ethernet switches and PoE support safer and power-efficient workspaces

As more companies look to reopen their facilities in the wake of the global health crisis, the latest PoE standards, along with modern Ethernet switches with advanced capabilities, can help ensure they're providing an intelligent work environment that's also safe for workers and customers.

For example, a smart building supported by the latest Ethernet switches could trigger an alert to a conference room, indicating that the room has reached maximum occupancy. Data from Ethernet switches could be used to guide people to other workspaces in the building, so they can adhere to social distancing guidelines.

If an organization is relying on outdated Ethernet switches, it won't be able to introduce capabilities that can help to create a safe, trusted workplace. It also won't be able to support Wi-Fi 6 or new wireless applications and devices that require more network bandwidth.

Also, it won't be able to make the most of PoE and use data collected by Ethernet switches to optimize their facilities to reduce power consumption and identify other measures that can help minimize their carbon footprint.

To ensure they're prepared for a much more connected, data-driven, and climate-focused future, organizations should modernize their Ethernet switches. In addition to implementing PoE switches and adopting the latest PoE standard, organizations will want to consider the options listed below.

Multigigabit Ethernet technology

In the past, existing cabling infrastructure could have prevented many businesses from taking advantage of Wi-Fi 6 and access points that require wireless bandwidth higher than 1 Gbps. Much of the cabling deployed worldwide is Cat 5e/6a and has been limited to 1 Gbps at 100 meters.

Multigigabit Ethernet technology enables speeds up to 10 Gbps on the same infrastructure without the need to replace cabling, while also providing up to 100W PoE on the same Multigigabit port.

See our Multigigabit Ethernet technology

Bandwidth levels

Bandwidth levels are another top consideration when choosing modern Ethernet switches.

For example, Ethernet switches support end-user access to networks and need a bandwidth level of 40 Gbps to transmit data and support uploads effectively. some Ethernet switches sit at the network core and manage all transportation within it. Those switches need to work at much higher speeds, so they require 100 Gbps.

Built-in security

Ethernet switches need to be secure. Malicious actors will look for security gaps in network devices like switches to enter a company's network. For example, they might hack into a building's unsecured, smart thermostat and then work to find a path to the company's financial systems.

Many of the latest Ethernet switches feature security mechanisms that are easy to use and keep up to date. Some also allow for segmentation, thus preventing situations like the one described above from happening by limiting what can be accessed on the network from the device.

Application hosting capabilities

Application hosting on an Ethernet switch is now possible with some modern switches. For example, a distributed computing application might be hosted on a switch in a smart building environment. This would allow the smart building to be more responsive.

For example, if someone enters a room with smart lighting, the lights could turn on immediately instead of a few seconds later. With an app hosted on a switch, there's no need to send data to the cloud and back, or to risk having slow response times because the network has many devices connected to it.

A critical investment for the future

Ethernet switches are more essential than ever, and they are much more than network hardware. They can make smart buildings not only smarter, but also transformative. Moreover, they can help organizations to increase IT and business resilience.

Ethernet switches are designed to be resilient. In fact, they were created to help organizations build strong, reliable networks that prevent data traffic collisions, ease bottlenecks, and help IT teams resolve performance issues more proactively.

With many people working remotely, it's an ideal time for businesses to think about upgrading their Ethernet hardware and software. Modernizing Ethernet switches and rethinking networks to support a digital future can be a complex undertaking that could require rewriting network plans or rebuilding networks.

This modernization is a necessary move for any business that wants to take advantage of next-generation Wi-Fi and create safe, secure, sustainable, and intuitive workspaces that allow them to optimize resources and reduce costs—as well as their carbon footprint.