|  | 7.4 | Layer 2 Devices
| 7.4.5 | Switches

Switching is a technology that alleviates congestion in Ethernet LANs by reducing traffic and increasing bandwidth. Switches, also referred to as LAN switches, often replace shared hubs and work with existing cable infrastructures to ensure they are installed with minimal disruption of existing networks.

Today, in data communications, all switching and routing equipment perform two basic operations:

1. switching data frames -- The process by which a frame is received on an input medium and then transmitted to an output medium.
2. maintenance of switching operations -- Switches build and maintain switching tables and search for loops. Routers build and maintain both routing tables and service tables.

Like bridges, switches connect LAN segments, use a table of MAC addresses to determine the segment on which a datagram needs to be transmitted, and reduce traffic. Switches operate at much higher speeds than bridges, and can support new functionality, such as virtual LANs.

An Ethernet switch has many benefits, such as allowing many users to communicate in parallel through the use of virtual circuits and dedicated network segments in a collision-free environment. This maximizes the bandwidth available on the shared medium. Another benefit is that moving to a switched LAN environment is very cost effective because existing hardware and cabling can be reused. Finally, network administrators have great flexibility in managing the network through the power of the switch and the software to configure the LAN.