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What’s a Layer 3 Switch?

A Layer 3 switch combines the local network connectivity of a traditional switch with the inter-network routing capabilities of a router in a single device. By using virtual routed ports internally, it enables communication between separate LANs without requiring dedicated routing hardware.

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About this video

Switches and routers have traditionally served distinct roles in network infrastructure. Switches operate at Layer 2 of the OSI model, connecting end devices within a local area network and enabling communication between hosts on the same network segment. Routers, by contrast, function at Layer 3, directing traffic between separate networks and making forwarding decisions based on IP addresses rather than MAC addresses. A Layer 3 switch bridges both functions within a single physical device. Rather than converting all ports to routed interfaces, it preserves standard Layer 2 connectivity for device interconnection while adding virtual routed ports internally. These virtual interfaces allow the switch to route traffic between different LANs without the need for a separate, dedicated router. This architecture makes Layer 3 switches a practical and cost-effective choice for environments where inter-VLAN routing is needed alongside high-density LAN connectivity. The emergence of Layer 3 switches reflects a broader trend in network design toward consolidating hardware and streamlining infrastructure. Understanding the distinction between a device's physical Layer 2 ports and its internal virtual routing capability is foundational to grasping how modern enterprise networks are built and managed.

What you'll learn

What's covered

Layer 3 Switch

Aligned to

CompTIA Network+
1.2 Compare and contrast networking appliances, applications, and functions.
2.2 Given a scenario, configure switching technologies and features.
Cisco CCNA
1.1 Explain the role and function of network components
Cisco CCST Networking
4.5 Explain basic switching concepts

Key terms

Layer 2
The Data Link layer of the OSI model, responsible for MAC addressing and frame delivery on a local network.
Layer 3
The Network layer of the OSI model, responsible for logical addressing and routing packets between networks.
Switch
A network device that connects devices within a LAN and forwards traffic based on MAC addresses.
Router
A network device that forwards data packets between networks based on IP addresses.
Layer 3 Switch
A network switch that incorporates routing functionality, allowing it to forward traffic based on both MAC addresses and IP addresses across multiple networks.
Virtual LAN
VLAN
A logical grouping of network devices that behave as if they are on the same network regardless of physical location.

Transcript

Here I have two different devices. I have a switch and a router, and traditionally they perform very different functions. Switching connects our end devices together so they can communicate on a local area network, versus a router, which interconnects those local area networks so that they can speak amongst different networks. So when we see ports on the switch, we think layer 2. These are layer 2 ports that can interconnect devices, versus the ports on the router, which are layer 3 ports that are routing between two different networks. That is the big difference.

Merging the two into one device

One of the things that's happened over time is that we've started merging equipment together. It's just more efficient to do it that way. What we've done is we've incorporated some of the functionality of a router into this switch right here.

So what does that look like? It's not our ports that are routed. We can actually make that happen, but for the most part, just think of these as all being layer 2 connectivity. And then on the back end, somewhere virtually inside of this, we create a routed port. We create one of these routed ports, but it's a virtual routed port inside of it that allows us to route from local area network to local area network.

We don't want to get too in depth into that. Just realize at this point in time that this is a layer 3 switch that incorporates some of the functionality of a router into this switch.

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