Tag Archives: Layer 3 Switch VS. Router

Can a Layer 3 Switch Be Used as a Router?

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With the development of technology, network switch grows not only in speed like the migration from gigabit Ethernet switch, to 10gb switch, 40gb switch and 100gb switch, but also in complexity to acquire more functions and meet complicated conditions. Layer 3 switch is equipped with advanced functions and is sometimes compared with a router by people. What are layer 3 switch and router? Can a layer 3 switch act as a router? This post will focus on this problem.

What Is Layer 3 Switch and How It Works?

The data switch is a layer 2 switching device that dynamically transmits packets according to the physical addresses (MAC addresses) of connected devices. Layer 3 switch, on the basis of the data switch, boasts additional routing decisions by inspecting the IP addresses. Layer 3 switches are thus able to segregate ports into separate virtual LANs (VLANs) and perform the routing between them. Additionally, this switch helps reduce the amount of broadcast traffic, simplify security management, and improve fault isolation.

layer 3 switch in networking

What Is Router and How It Works?

A router works at layer 3 of the OSI Model (Network). It is a device usually located at gateways where networks meet, to connect various local networks and wide networks. It decides where to send packets by utilizing an IP Routing table. When an IP packet comes in, the router looks up the destination IP in the IP Routing table. If that destination IP is not found in the table, the router will drop the packet.
The router can perform NAT to translate the private IP address to public address, which can get you into the Internet. So it is a common network device in household use.

Can a Layer 3 Switch Be Used as a Router?

As a layer 3 switch possesses the routing function of a router, can we replace a router with it? Let’ s have a detailed view of their similarities and disparities.

Layer 3 Switch Vs Router

Layer 3 Switch Vs Router: Similarity

Both layer 3 switch and router work at layer 3 of the network. Layer 3 switches technically have a lot in common with traditional routers. Both of them can support the same routing protocols, inspect incoming packets and make dynamic routing decisions based on the source and destination addresses inside. The switches can also be configured to support routing protocols such as RIP, OSPF, and EIGRP.

Layer 3 Switch Vs Router: Disparity

Internally, the hardware inside a layer 3 switch blends that of traditional switches and routers. As for packet forwarding, router transmits packet by a microprocessor-based software routing engine, while the switch performs switching through hardware. After routing the first data flow, the layer 3 switch will generate a mapping table of MAC addresses and IP addresses, so that the same data flow will directly pass through the layer 2 according to this table, thus eliminating network delay and improving the efficiency of packet forwarding. Externally, layer 3 switches do not offer the WAN-type ports as standard routers do, so they lack WAN functionality.

Router requires configurations before deployment due to the inbuilt operating system. On the contrary, the layer 3 switch is usually ready to go when acquired, and configurations are optional as you like.

From a software perspective, layer 3 switches are not capable of the extra services that routers typically provide, such as NAT and NetFlow.

Conclusion

All in all, it is not recommended to replace a router with layer 3 switch, but you can apply them in the same network at the same time. In addition, whether a layer 3 switch can supplant a router relies upon the switch model and what you expect from it. Some layer 3 switches are almost router substitutions, with a full scope of WAN, firewall, VoIP, and so on. However, those switches are costly, and most layer 3 switches just have Ethernet ports. In this way, a dedicated router is cost-effective than a layer 3 switch.

Layer 3 Switch VS. Router

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In the OSI model, we know that traditional network switch operates at Layer 2 while network routers operate at Layer 3. Besides, switches are understood to be forward traffic based on MAC address, while routers perform the forwarding based on IP address. Layer 3 switches have a lot in common with traditional routers: they can also support the same routing protocols, inspect incoming packets and make dynamic routing decisions based on the source and destination addresses inside. For this reason, many networking beginners are puzzled over the definition and purpose of a Layer 3 switch. So what is on earth Layer 3 switch and what is the difference between Layer 3 switch vs. router?

Layer 3 Switch

Layer 3 switch is also called multilayer switch. It is a specialized hardware device used in network routing, which is conceived as a technology to improve network routing performance on large local area networks (LANs) like corporate intranets. A Layer 3 switch is both a switch and a router. So Layer 3 switch is a switch that can route traffic, and a router with multiple Ethernet ports has a switching functionality. It can switch packets by checking both IP addresses and MAC addresses. On this account, Layer 3 switches separates ports into VLANs and perform the routing between them, in addition to supporting routing protocols such as RIP, OSPF and EIGRP.

Layer 3 switch

Layer 3 Switch VS. Router

From the basics of Layer 3 switch, it may seem to perform the same functionality with the router. In fact, they have some key distinction facts. The key differences between Layer 3 switches and routers lay in the hardware technology used to build the unit. The hardware inside a Layer 3 switch merges that of traditional switches and routers, replacing some of a router’s software logic with hardware to offer better performance in some situations. The table below illustrates the differences between Layer 3 switch and router.

Layer 3 Switch VS. Router

Layer 3 Switch vs. Router: Main Differences:
  • Cost – Layer 3 switch is much more cost effective than router for delivering high-speed inter-VLAN routing. High performance router is typically much more expensive than Layer 3 switch.
  • Port density – Layer 3 switch has much higher port count while router has a lower port density than Layer 3 switch.
  • Flexibility – Layer 3 switch allows you to mix and match Layer 2 and Layer 3 switching. It means that you can configure a Layer 3 switch to operate as a normal Layer 2 switch.
  • WAN technologies support – Layer 3 switch is limited to usage over LAN environment where Inter VLAN routing can be performed. However, when it comes to working on WAN and edge technologies, Layer 3 switch lags behind. Router is the front runner in such scenario where WAN technologies such as Frame Relay or ATM need to be fostered.
  • Hardware/Software decision making – The key difference between Layer 3 switch and router lies in the hardware technology used to making forwarding decision. Layer 3 switch uses ASICs for forwarding decisions. Conversely, the router makes forwarding decisions based on hierarchical Layer-3 addresses.
Layer 3 Switch with VLANs

As here is mentioned the VLAN, so let’s talk about it firstly. A VLAN (virtual LAN) is a logical subnetwork that can group together a collection of devices from different physical LANs. VLANs can improve the overall performance of busy networks. So they are often set up for improved traffic management by larger business computer networks. With a VLAN, traffic can be handled more efficiently by network switches.

Each virtual LAN must be entered and port-mapped on the switch. Routing parameters for each VLAN interface must also be specified. Some Layer 3 switches implement DHCP support that can be used to automatically assign IP addresses to devices within a VLAN. Alternatively, an outside DHCP server can be used, or static IP addresses configured separately. The diagram below shows an example of a layer 3 switching routing between VLANs through its two VLAN interfaces.

Layer 3 Switch with VLAN

These switches are most commonly used to support routing between virtual LANs (VLANs). Benefits of Layer 3 switches for VLANs include:

  • Reduction in the amount of broadcast traffic
  • Simplified security management
  • Improved fault isolation
Conclusion

From what we have discussed about Layer 3 switch vs. router, Layer 3 switch may be more preferable in result of its capability of routing and switching. Besides, it can perform as a top of rack device and a distributed core switching layer at the same time. This reduces the L2 complexity of the client access layer, which makes the network more reliable and easier to manage. FS.COM can provide a comprehensive, scalable and secure portfolio of switches for enterprise and service provider networks. There are also a huge stock of compatible fiber optic transceivers and cables. For more details, please visit www.fs.com.