#13: What Is a Switch?

But here's something to think about.

Imagine a computer lab with twenty computers, several printers, and a server. All these devices need to communicate with each other.

How can they connect to the same local network and exchange data efficiently?

One important device that makes this possible is a network switch.

Let's understand what a switch does, how it works, and why it matters.

What Is a Network Switch?

A network switch is a device that connects multiple devices within a local area network (LAN) and forwards data to the appropriate destination.

These devices might include:

• Computers
• Printers
• Servers
• Network storage devices
• Other Ethernet-connected equipment

A switch allows connected devices to communicate over the same local network.

For example, imagine an office where ten computers are connected to a switch using Ethernet cables. The switch helps these computers exchange data without requiring a separate direct cable between every pair of computers.

This makes connecting multiple devices much more practical.

Why Do We Need a Switch?

Imagine you have five computers in a computer lab.

Each computer needs to communicate with other devices on the network. Perhaps the students need to access a shared printer or retrieve files from a local server.

Connecting every computer directly to every other computer would quickly become complicated.

A switch provides a central connection point.

Each computer connects to the switch, and the switch forwards network traffic toward the appropriate destination.

The basic arrangement looks like this:

Computer A → Switch ← Computer B

Other devices, such as printers and servers, can connect to the same switch.

This arrangement makes it easier to expand and manage a local network.

How Does a Switch Work?

To understand a switch, let's follow a simple example.

Imagine Computer A wants to send data to Computer B. Both computers are connected to the same local network through a switch.

Step 1: Computer A prepares the data

Computer A creates network traffic intended for Computer B.

On a typical Ethernet LAN, the data is carried inside an Ethernet frame.

Step 2: The frame reaches the switch

The switch receives the Ethernet frame through the port connected to Computer A.

A port is the connection point where a network cable or device connects to the switch.

Step 3: The switch checks the destination MAC address

The switch examines the destination MAC address in the Ethernet frame.

A MAC address is a hardware-level address associated with a network interface. We explored MAC addresses earlier in this series.

Step 4: The switch forwards the frame

The switch uses its MAC address table to determine which port leads toward the destination.

If it knows the correct port, it forwards the frame through that port rather than sending it to every connected device.

Step 5: Computer B receives the data

The frame reaches Computer B, allowing the communication to continue.

The exact behavior depends on the frame and the switch's current information, but this is the basic process.

What Is a MAC Address Table?

A switch needs a way to learn which devices can be reached through its ports.

It does this by building and maintaining a MAC address table.

This table associates learned MAC addresses with the switch ports through which those addresses can be reached.

For example, imagine a switch has three connected computers.

Computer A connects to Port 1.

Computer B connects to Port 2.

Computer C connects to Port 3.

As the switch receives frames from these devices, it learns their source MAC addresses and associates them with the relevant ports.

When a frame arrives, the switch can use its table to help decide where to forward it.

You don't need to memorize the technical details yet. Just remember:

The MAC address table helps a switch identify which port can reach a particular device.

Does a Switch Always Send Data to Every Device?

No.

When a switch knows the appropriate destination port for a unicast frame, it normally forwards that frame only through the relevant port.

This helps avoid unnecessarily sending the same traffic to every connected device.

However, if the destination MAC address is unknown, a switch may flood the frame through other eligible ports within the same VLAN, excluding the port where the frame arrived.

Certain other types of Ethernet traffic, such as broadcasts, are also distributed to multiple eligible ports.

For now, the key idea is that a switch learns where devices are connected and uses that information to forward traffic appropriately.

What Is the Difference Between a Switch and a Router?

Switches and routers are both essential networking devices, but their primary jobs are different.

A switch connects devices within a local network and commonly forwards Ethernet frames based on MAC addresses.

A router forwards IP packets between different IP networks using routing information.

Let's consider a practical example.

Your laptop and printer are connected to the same office network. A switch helps carry local network traffic between them.

Now imagine your laptop wants to open a website hosted on the internet.

If the website is outside your local network, your laptop typically sends the traffic toward its default gateway, often a router.

The router forwards that traffic toward the destination network.

In simple terms:

Switch → Connects devices within a local network

Router → Forwards traffic between networks

Their functions are different, but they often work together.

Can a Switch Connect to a Router?

Yes. In fact, this is common in home and business networks.

Imagine an office network with several computers.

Each computer connects to a switch. The switch then connects to a router, which provides a path to other networks.

The layout might look like this:

Computer A ─┐

Computer B ─┼→ Switch → Router → Internet

Computer C ─┘

The switch helps the computers connect to the local network.

The router allows traffic to move beyond that network.

A switch doesn't have to connect directly to the internet to help devices communicate locally.

Do All Switches Look the Same?

No. Switches come in different sizes and have different capabilities.

Some have only a few Ethernet ports and are suitable for small networks.

Others have dozens of ports and are designed for offices, universities, data centers, and other larger environments.

Some switches are unmanaged, meaning they require little configuration.

Others are managed, allowing network administrators to configure and monitor features such as VLANs, traffic prioritization, and port settings.

We won't explore those advanced features in detail yet. For now, the important point is that switches can be simple or highly configurable depending on the network's needs.

Does a Switch Provide Wi-Fi?

A standard Ethernet switch usually connects devices through wired network connections. It does not automatically provide wireless connectivity.

For Wi-Fi, a network commonly uses a wireless access point.

Some home networking products combine switching, routing, and wireless access point functions inside one physical device. That is why the different networking roles can sometimes seem confusing.

Remember that a single box may perform several functions, even though those functions are conceptually different.

Why Are Switches Important in Cybersecurity?

Switches are part of the infrastructure that carries data through local networks.

Understanding them helps cybersecurity learners understand where devices connect and how local traffic moves.

Managed switches can also support security-related features, such as separating devices into VLANs, limiting access to switch ports, and monitoring certain network activity.

However, a switch alone does not make a network secure. Its security depends on the model, configuration, surrounding network design, and other protective controls.

At the foundation level, simply understanding how devices connect and how traffic reaches its destination gives you a stronger basis for learning network security later.

Bringing It All Together

Let's connect this article with what we've already learned.

A device has an IP address used for communication at the IP layer.

Its network interface also has a MAC address used in local Ethernet communication.

When devices communicate over an Ethernet LAN, a switch can use MAC addresses to forward Ethernet frames through the appropriate ports.

When traffic needs to reach a destination on another IP network, the device typically sends it toward its default gateway, often a router.

These devices perform different jobs, but they work together to support network communication.

Final Takeaway

A network switch connects devices within a local area network and forwards Ethernet frames toward the appropriate destination.

It learns MAC addresses and associates them with switch ports, helping data reach the correct device.

You don't need to learn advanced switch configuration yet.

For now, remember:

A switch helps devices communicate within a local network. A router helps traffic move between different networks.