What Is the Function of a Switch in a Computer Network?

Connecting a few devices to a switch allows them to start communicating over the network immediately. But a network switch does more than just connect cables. It keeps your file transfers and video calls running smoothly. It determines where each piece of data needs to go and sends it there. It appears simple, but there's more happening behind the scenes.

So what is the true function of a switch within a computer network? This guide explains how a switch learns device addresses and forwards data, as well as manages network traffic, covering everything from small home networks to large business networks.

The Basic Function of a Switch

A switch primarily connects various devices, from computers to cameras, and enables them to communicate over a shared network. That is the basic job of a switch and sounds nothing special. 

One of the key uses of network switches is directing data to the correct connected device. A switch identifies the target device and forwards the data directly to it instead of broadcasting it to every device on the network, improving network efficiency and reducing unnecessary traffic. All other network devices continue working independently and handle their own traffic.

How a Switch Determines Data Routing

But does a switch know where everything is right from the beginning? No! A switch does not come with pre-configured settings to recognize which device is connected to each port. 

Step 1: Frame Arrives

A device sends data, and it enters the switch through a specific port.

Step 2: The Switch Reads the Source Address

Each device possesses a unique MAC address. The switch records which port the address came from and adds it to a MAC address table. 

Step 3: The Switch Verifies the Destination

If it already knows the port for the destination device from an earlier frame, it sends the data there.

Step 4: If the Destination is Unknown, It Results in Flooding

The switch sends the data out of every port except the one it came from until the correct device responds. After that, it knows where to send data for that device.

This table gradually fills with almost every device on the network, causing the switch to stop flooding almost completely. 

For example, a person is directing visitors to the right room in a building. The first time, they need to check where each person belongs. Once they know where everyone is, they can send each person to the right place without checking every room again. A switch works in much the same way, just thousands of times per second. It keeps learning and updating this information as devices connect and disconnect.

How Switches Actually Move Data Internally

You’ll see switches sometimes explained and compared to terms like circuit switching or message switching. That's not quite right. An Ethernet switch works differently. There are three main forwarding methods among Ethernet switches.

• Store-and-forward: The switch receives the entire frame and verifies it for errors before forwarding it. It also drops damaged frames instead of passing them further. Though the process is slightly slower, it is more reliable.

• Cut-through: In this method, the switch reads the destination address first. After that, it begins forwarding the frame without waiting for the entire frame to arrive. This makes it faster, but it can sometimes forward corrupted data as well.

• Fragment-free: This mode lies between the two methods. The switch delays and examines the first 64 bytes for errors before forwarding the frame.

Most modern switches are configured to operate in store-and-forward mode by default. When you configure a network switch, this mode helps prioritize data accuracy and error checking over raw switching speed, making it suitable for well-designed business networks.

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Function of a Switch vs. a Hub

Old networks used hubs. But hubs had one major flaw. They transmitted all incoming signals to every connected port, ensuring none were missed. If a single hub has ten devices connected to it, they would share the same bandwidth. That also caused frequent signal collisions whenever two devices transmitted data together.

A switch addresses both issues in one go. Each port becomes its own private connection. That means the collisions between devices connected to different ports are avoided. The main reason switches completely replaced hubs is not due to poor quality of hubs, but because switches are inherently more intelligent in managing traffic.

Function of a Switch vs. a Router: Where the Job Actually Splits

People frequently confuse switches with routers. A switch connects devices on a local network, while a router links different networks, typically connecting your local network to the internet. Switches recognize devices via their MAC addresses and mainly work at Layer 2 of the OSI model. But routers identify IP addresses and work at Layer 3. Some advanced switches, known as Layer 3 switches, can perform both roles. That means they can manage local traffic and routing between subnets or VLANs. However, the main purpose of a standard switch is the same. It efficiently directs data to the correct device within the same local network, minimizing unnecessary traffic.

Managed vs. Unmanaged Switch: Does the Core Function Change?

An unmanaged switch automatically handles all mentioned functions without needing any configuration. Once plugged in, it works right away. This makes it ideal for home networks and small setups.

A managed switch performs the same basic function but gives administrators far more control over how it’ll be done. For instance, VLANs let you segment traffic into isolated groups. You can also prioritize sensitive traffic, such as video calls, over background downloads using Quality of Service (QoS). Plus, port-level security makes it easy to lock down which devices are allowed to connect in the first place.

Small office or home setups mostly need the basic functions of a switch. But growing networks with cameras, VoIP phones, and multiple departments need that added control. 

Where This Function Actually Matters in Real Deployments

Switches don't work alone in large networks. They're typically organized in a layered structure:

• Access layer: This refers to where end devices—computers and cameras—are plugged in.

• Distribution layer: This layer consolidates traffic from various access switches and implements policies like VLAN routing.

• Core layer: This is the high-speed backbone, and it transports large volumes of traffic among all other networks.

At its core, a switch simply learns addresses and forwards data accordingly. This simple job holds up the same at a large scale when the switches are organized properly. Sure, you can throw a bunch of devices on one flat switch, and it'll work fine for a small setup. But once you're talking hundreds or thousands of devices, that structure is what keeps things from falling apart.

Troubleshooting is also part of managing such setups. With this configuration, troubleshooting can be easier. For example, if something goes wrong at the access layer, the issue is usually limited to that section. It’ll not bring down the entire network. But losing a core switch can affect a much larger part of the network. So, core-layer hardware includes redundancy features such as backup power supplies and failover links. These features help prevent a single failure from taking the whole network offline.

Power over Ethernet, or PoE, gives switches another useful feature too. PoE-capable switches send both data and electrical power through the same cable. Security cameras and wireless access points can therefore work without a separate power outlet.

Choosing a Switch Based on What You Actually Need It to Do

Selecting a switch becomes simpler once you understand the function of a switch and the factors that need to be considered. Start by asking yourself a few questions.

• How many devices do you actually need to connect?

• Do you require traffic separation for different departments or device types?

• Do any connected devices, such as cameras or access points, require power over the same cable?

A simple unmanaged switch is common in home networks. But offices handling security systems and VoIP phones, alongside an increasing number of staff devices, find a managed switch with VLAN and QoS support generally more suitable. Larger deployments can use Layer 3 switches because they provide fast routing between different network segments.

Wrapping Up

The function of a switch includes one core skill: It learns where devices live on a network and sends data to the right place, instead of everywhere at once. All other features such as VLANs, QoS, PoE, and Layer 3 routing are built upon this fundamental function.

Remember this basic idea, and you can easily choose a switch based on your network needs. From there, choose a switch that handles the basic job and has the extra features your setup requires.

Get the Right Network Switch with Ultra Tech

Looking for a network switch for your home, office, or business network? Setting up a new network or upgrading the current one? Ultra Tech is among the top network switch providers, offering a range of MikroTik switches, from simple unmanaged models to advanced Layer 3 switches. Whether you are setting up a small network or managing a larger infrastructure, our range includes options for different network sizes, connected devices, and feature requirements.