Switching grew out of the need for increased network bandwidth. Various network topologies exist today, but Ethernet, as defined by the various IEEE 802.3 standards, accounts for the vast majority of current LANs. The original Ethernet installations required snaking cables between computers in a bus topology. The introduction of Ethernet hubs allows for installations that look like a star topology, but actually still act as a linear bus. This allowed network engineers to increase the size of the networks.

Ethernet works on CSMA/CD, which means that too many stations connected with hubs will adversely affect the performance of the entire network since they all belong to the same collision domain. The invention of the switch allows network engineers to split the network into multiple segments, with each segment acting as an individual collision domain.

The first switches were little more than ASICs acting as transparent bridges. Traditional switches work entirely on Layer 2 of the OSI Reference Model, using MAC addresses to forward frames between network devices. Even though switches eliminate collisions, they do not eliminate broadcasts. Broadcasts, whether at Layer 2 or Layer 3, generally consist of service requests flooded over an entire network. All machines participating in this exchange of flooded frames and packets belong to a single broadcast domain. A network experiences a broadcast storm when the sheer volume of broadcasts prevents other information from passing between the devices.

Routers, working at Layer 3 of the OSI model, kill broadcasts by splitting a LAN into multiple...