A switch is a device which sends a data packet in a local network. What is advantage over hub? A hub floods the network with the packet and only 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 network just like hub to fill MAC- address table, on which port a particular device is connected. After learning it sends packets to that particular host only.
A L2 switch does switching only. This means that it uses MAC addresses to switch the packets from a port to the destination port (and only the destination port). It, therefore, maintains a MAC address table so that it can remember which ports have which MAC address associated.
A L3 switch also does switching exactly like a L2 switch. The L3 means that it has an identity from the L3 layer. Practically this means that a L3 switch is capable of having IP addresses and doing routing. For intra-VLAN communication, it uses the MAC address table. For extra-VLAN communication, it uses the IP routing table.
This is simple but you could say “Hey but my Cisco 2960 is a L2 switch and it has a VLAN interface with an IP !“. You are perfectly right but that VLAN interface cannot be used for IP routing since the switch does not maintain an IP routing table.
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.
|LAYER 2 SWITCH||LAYER 3 SWICTH|
|Operate on layer 2 (Data link) of OSI model.||Operate on layer 3 (Network Layer) of OSI model.|
|Send “frames” to detination on the basis of MAC address.||Route Packet with help of IP address|
|Work with MAC address only||Can perform functioning of both 2 layer and 3 layer switch|
|Used to reduce traffic on local network.||Mostly Used to implement VLAN (Virtual Local area network)|
|Quite fast as they do not look at the Layer 3 portion of the data packets.||Takes time to examine data packets before sending them to their destination|
|It has single broadcast domain||It has multiple broadcast domain.|
|Can communicate within a network only.||Can communicate within or outside network.|