Difference between layer-2 and layer-3 switches

A switch is a device that sends a data packet to a local network. What is the advantage of a hub? A hub floods the network with the packet and only the destination system receives that packet while others just drop due to which the traffic increases a lot. To solve this problem switch came into the picture. A switch first learns, by flooding the network just like a hub to fill the MAC- address table, on which port a particular device is connected. After learning it sends packets to that particular host only. 

What is a Layer-2 Switch?

A Layer-2 switch works at the Data Link layer or Layer 2 of the OSI reference model. It especially utilizes MAC addresses to direct information packets between devices that are on the exact same network.

• MAC Address Table: A Layer-2 switch will keep a MAC address table that identifies the MAC address of the connected device and the port number. This enables the switch to direct frames towards the correct destination.
• VLAN Support: Layer-2 switches can support VLANs (Virtual Local Area Networks), which means that the network can be segmented at this layer.
• Switching Frames: These forward Ethernet frames are according to MAC addresses and are vital in minimizing collision within LANs.
• Broadcast Domains: Layer-2 switches do not partition broadcast domains, all the devices connected to a Layer-2 switch are in the same broadcast domain.

What is a Layer-3 Switch?

A Layer-3 switch works at the third layer of the OSI mode and it has features of both a switch and a router. It employs IP addresses in the forwarding of packets and routing among one or different networks/subnets. Layer-3 switches are characterized by:

• Routing Capabilities: Layer – 3 switches are different from Layer – 2 switches in that Layer – 3 switches are capable of routing by inspecting the IP headers of the packets and computing the best path for the data.
• Inter-VLAN Routing: Layer-3 switches can also forward traffic between VLANs, but this is often needed only in larger networks where segmentation has to be performed.
• Reduced Latency: Due to FULL layer routing implementation, this means that Layer-3 switches can avoid having to use a different router hence improving on the existing less latency in the networks.
• Advanced Features: Layer-3 switches are usually equipped with features such as ACL and QoS among others in the process of managing the switches.

Layer 2 switch work on layer 2 of OSI model i.e. data link layer and sends a "Frames" to destination port using MAC address table which stores the mac address of a device associated with that port. Layer 3 switch work on layer 3 of OSI model i.e. network layer where it route packet by using IP address, it is used widely on VLANs.

Difference Between Layer-2 and Layer-3 Switches

Conclusion

Thus, Layer-2 and Layer-3 switches can be defined in terms of their functional layers and activities. In simple LAN network which involves a basic level of network segmentation, Layer-2 switches are preferred while for more complex network especially those involving routing and inter VLAN, Layer-3 switches are preferred. A switch is therefore dictated by the requirement and the size of the network you intend to connect.

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Article Tags :

• Misc
• Computer Networks
• GATE CS

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