Layer 3 Switch: Uses, Pros, and Cons

In network design, there is often a battle for resources. Networks seem to constantly face larger volumes of traffic and greater demands on bandwidth. Juggling more connections usually slows the network down considerably, and that leads to the struggle. How do you handle increased traffic without sacrificing performance? In some networks, Layer 3 switches can improve traffic management while also increasing net performance.

What Is Layer 3?

The simplest explanation possible is that a Layer 3 switch is a single device that works as a switch and router. More specifically, it’s a device that uses routing intelligence to provide switching in Layer 3 of the OSI model.

This primarily means two things for Layer 3 switching. First, it is still a switch and is not providing WAN services. Second, it thrives in traffic management for VLANs.

What Is the Purpose of Layer 3 Switching?

The primary reason for Layer 3 switching is better management of large traffic volumes. Layer 2 switching is very fast, but it is prone to hanging when there is too much traffic. Routing intelligence can handle more traffic, but it doesn’t function inside Layer 2.

You could simply add routers to a network, but that creates another communication node between endpoints, and it slows traffic as a result.

Layer 3 switching is a solution that allows router-level intelligence for traffic management with the speed of switching. You get better overall performance with Layer 3 switching, provided the network is a good use case.

What Are Some of the Key Features?

In order to fill its dual role, a Layer 3 switch will incorporate static and dynamic routing. This allows a single switch to support multiple VLANs, and it allows for optimal packet routing. That extends to faster communication within the network, and these features enable the Layer 3 switch to manage large volumes of traffic very efficiently.

Many Layer 3 switches also provide additional data security, such as loopback detection.

Pros of Layer 3 Switching

Layer 3 switching offers a few clear advantages for network design.

Improved fault isolation leads to better stability, even when traffic is dense and demanding. Security is also simpler in Layer 3, so this type of switching is ideal when a network requires greater security with less effort.

Layer 3 switching is designed for efficiency, which helps with reducing broadcast traffic volumes. The efficiency also lends to easier VLAN configurations. On top of that, removing routers from each VLAN dramatically simplifies VLAN incorporation.

Layer 3 switches additionally provide separate routing tables and lower latency by removing independent routers from the setup.

Cons of Layer 3 Switching

Despite those many advantages, Layer 3 switches are not ideal for all networks. The primary drawback to this technology is the cost. Layer 3 switches typically cost much more than routers, so when the specific performance advantages of Layer 3 switching are not needed, the devices are cost-prohibitive.

Layer 3 switching is also slower than Layer 2 switching. So, if network density doesn’t necessitate switching in Layer 3, then it’s an unnecessary cost that also lowers overall performance.

Finally, with Layer 3 switching, VLANs are married to a single switch. That can make VLAN planning a lot more challenging.

Common Applications

Ultimately, Layer 3 switching appears in a number of applications that have a few traits in common. It is ideal for large intranets, so you will find Layer 3 switching on campuses, in data centers, and across large enterprise organizations. It handles traffic density well within the intranet for each of these scenarios.

Layer 3 switching is also ideal for fast-growing enterprises. The Layer 3 switching model can use bandwidth more efficiently, which enables it to grow with an enterprise more efficiently.

Lastly, Layer 3 switches are often used for long-distance data transmission. Very large intranets still benefit from Layer 3 switching, making the devices common in these applications.

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• Cisco Catalyst Switches Product Guide
• Basics of Network Switches
• What are the Differences between Cisco 3650 and 3750X Switches?
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