LAN switching

LAN switching is a form of packet switching used in local area networks (LAN). Switching technologies are crucial to network design, as they allow traffic to be sent only where it is needed in most cases, using fast, hardware-based methods. LAN switching uses different kinds of network switches. A standard switch is known as a layer 2 switch and is commonly found in nearly any LAN. Layer 3 or layer 4 switches require advanced technology (see managed switch) and are more expensive, and thus are usually only found in larger LANs or in special network environments.

Layer 2 switching uses the media access control address (MAC address) from the host's network interface cards (NICs) to decide where to forward frames. Layer 2 switching is hardware-based, which means switches use application-specific integrated circuit (ASICs) to build and maintain filter tables (also known as MAC address tables or CAM tables). One way to think of a layer 2 switch is as multiport bridge.

Layer 2 switching provides the following

Layer 2 switching is highly efficient because there is no modification to the data packet and the frame, encapsulation of the packet changes only when the data packet is passing through dissimilar media (such as from Ethernet to FDDI). Layer 2 switching is used for work group connectivity and network segmentation (breaking up collision domains). This allows a flatter network design with more network segments than traditional networks joined by repeater hubs and routers. Layer 2 switching has helped develop new components in the network infrastructure.

These new technologies allow more data to flow off from local subnets and onto a routed network, where a router's performance can become the bottleneck.

...
Wikipedia