An Ethernet switch has a structure where each port is directly connected to a host, and it typically operates in full-duplex mode. A switch can connect many pairs of ports simultaneously, allowing each pair of communicating hosts to transmit data without collisions, as if they had exclusive access to the communication medium. So, how do Ethernet switches work? Let's take a closer look!
Ethernet switch working principle
Ethernet switches operate at Layer 2 (data link layer) of the OSI network reference model. They are network devices that use MAC (Media Access Control) address recognition to forward Ethernet data frames.
The ports on a switch used to connect computers or other devices are called ports. Computers connect to these ports via network cards (NICs) using network cables. Each port on a NIC, switch, or router has a MAC address, which is permanently stored in the device's EPROM by the manufacturer. MAC addresses are assigned by the IEEE, and each MAC address is globally unique. A MAC address is a 48-bit binary number; the first 24 bits are used to identify the device manufacturer, and the last 24 bits are a serial number assigned by the manufacturer.
A switch receives data frames sent by a computer on its port, looks up the MAC address in its MAC address table based on the destination MAC address in the frame header, and then forwards the data frame out from the corresponding port, thereby achieving data exchange.
The working process of a switch can be summarized as "learning, memorizing, receiving, looking up, and forwarding": Through "learning," it can learn the MAC address of the device connected to each port; it "memorizes" the correspondence between MAC addresses and port numbers in memory, generating a MAC address table; after "receiving" a data frame from a port, it "looks up" the port number corresponding to the destination MAC address in the frame header in the MAC address table, and then "forwards" the data frame out from the found port.
Switches divide collision domains, with each port forming its own independent collision domain. If a port has a large amount of data to send, it will first store the received data waiting to be sent in a register, and then send it out when it is its turn to send.
