The switch, much like the router (and not the Nintendo kind), interconnects devices allowing them to communicate. It handles all internal networking traffic and directs it to the proper location using packet switching; however, it only connects devices on the same network.
A Very Brief History
It can be hard to pin down an exact date of the first switch, however, it was sometime in the late 80s and early 90s. The switch was developed to replace the quickly aging network hub as a far superior solution. By the early 2000s a switch was at the same price point as the hub and the internet didn’t look back.1ATPM: How to Become a Network Guru
How It Works
The magic sauce behind a switch is the MAC address table. The table is composed of all devices known to the switch and what port they can be found on. When a data packet is sent to the switch, it checks if the destination is in the table. If so, the packet is forwarded out only the designated port for the device. However, if the device is unknown, an ARP Request is broadcast out all ports.
Why Do We Need Them?
Switches are used to expand or extend existing networks. A network is limited primarily by two factors: the limited number of physical ports and the amount of IP Addresses available. Luckily a simple switch can help with the lack of physical ports issue. By adding a switch, a network can be expanded to accommodate more devices.
When purchasing switches, it is important to note one port will be used to connect to your existing network. For example if you buy an eight port switch, only seven ports will be available for new devices. Make sure you purchase one that meets your current needs and possible future expansion.
Balancing price and speed is always a concern when purchasing networking equipment, and switches are no different. Most of our homes have 1Gbps connections throughout, and devices to go with it. While 1Gbps switches are more expensive, the cost is negligible and future proofing is always a good idea. Luckily, switches auto negotiate the connection speed used with a device. Plugging a slower 100Mbps device into a 1Gbps switch will work properly, albeit at the slower 100Mbps speed.