A Layer 3 switch is a special hardware device used for network routing. Layer 3 switches are technically very similar to traditional routers. Both can support the same routing protocols, check incoming packets, and perform dynamic routing based on source and destination addresses.
One of the main advantages of a Layer 3 switch over a router is the way in which routing decisions are made. Because packets in a path require fewer extra steps, network latency switches are far less likely.
The purpose of layer 3 switches
Layer 3 switches were intended as a technology to improve network routing performance on large-scale local area networks such as enterprise intranets.
The main difference between Layer 3 switches and routers is their internal hardware. The hardware inside a Layer 3 switch is a combination of traditional switches and routers that provide better performance for local area networks by replacing some router software logic with integrated circuit hardware.
In addition, a Layer 3 switch will typically not have WAN ports and related capabilities when designed for use in intranets. These switches are often used to support routing between virtual local area networks (VLANs). The benefits of Layer 3 switches for VLANs include:
- Reduce the amount of traffic released
- Simplify security management
- Improved fault isolation
How Layer 3 Switches Work
A traditional switch dynamically shifts traffic between each of the physical ports to the physical addresses (MAC addresses) of connected devices. Layer 3 switches use this feature when managing traffic within the local network.
They also increase network capability by using IP address information to make routing decisions when managing traffic between local networks. In contrast, Layer 4 switches also use UDP or TCP port numbers.
Use Layer 3 switches with virtual LAN
Each virtual LAN and port map must be entered in this switch. Routing parameters for each VLAN interface must also be specified.
Some Layer 3 switches also support DHCP, which can be used to automate the assignment of IP addresses to devices on a VPN. An alternative DHCP server or statically set IP addresses can also be used as an alternative.
Problems with Layer 3 switches
Layer 3 switches cost more than traditional switches but less than traditional routers. Configuring and managing these switches and VLANs also requires more effort. The applications of Layer 3 switches are limited to intranet environments with devices and traffic large enough. Home networks do not usually use these devices. Lack of WAN capability makes it impossible to replace Layer 3 switches with routers.
The name of this type of switches is based on the concepts of the OSI model, in which layer 3 means network layer.
Unfortunately, this theoretical model does not show the practical differences between industrial products well. And this naming has caused confusion in the market.