How does an Ethernet switch work?

Ethernet switches, both unmanaged and managed, avoid collisions by routing the messages in an Ethernet network to only the intended devices. When a switch receives an Ethernet message (packet), it reads the address of the device for which the message is intended, and then transmits the message out of only the port to which that device is connected (even if it is connected through several other switches).

When the switch gets the first bit of information from the first device, such as your computer, it reads the MAC address of that device. The MAC address is the media access control number. This number is an ID number that is assigned to most network adapters and is preset by the manufacturer. Once this number is read, it is recorded in memory by the switch. Next, the switch attempts to look for any other devices on the network by sending out packet requests of information. Once another device gets this packet, it sends out a signal to the switch to acknowledge the request. Now the MAC address of this device is recorded. Each time these packets are sent, the information is "time stamped." The switch then works to filter this information that is communicated among all of the devices. The switch has enough memory to retain this information.

Industrial applications of Ethernet (called industrial Ethernet) require special Ethernet switches that have industrial ratings for noise immunity, shock, vibration and temperature in a wide range of form factors with multiple options for copper and fiber connectivity. See link below for examples of industrial Ethernet Switches from Phoenix Contact.