What is the function of switch

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The main functions of the switch include physical addressing, network topology, error checking, frame sequence and flow control. The switch also has some new functions, such as VLAN (virtual local area network) support, link aggregation support, and even firewall function.
The history of electrical signal exchange should be traced back to the early days of telephone. When the telephone was invented, only a long enough wire and two telephones at the end were needed to enable two people far away to have a voice conversation.
In addition to being able to connect the same type of network, switches can also interconnect different types of networks (such as Ethernet and fast Ethernet). Nowadays, many switches can provide high-speed connection ports supporting fast Ethernet or FDDI, which can be used to connect other switches in the network or provide additional bandwidth for key servers with large bandwidth consumption.
Generally speaking, each port of the switch is used to connect an independent network segment, but sometimes in order to provide faster access speed, we can connect some important network computers directly to the port of the switch. In this way, the key servers and important users of the network will have faster access speed and support greater information flow.
Learning function: the Ethernet switch understands the MAC address of the device connected to each port, maps the address with the corresponding port, and stores it in the MAC address table in the switch cache.
Forwarding filtering: when the destination address of a data frame is mapped in the MAC address table, it is forwarded to the port connecting the destination node instead of all ports (if the data frame is a broadcast / multicast frame, it is forwarded to all ports).
Elimination of loop: when the switch includes a redundant loop, the Ethernet switch avoids the generation of loop through spanning tree protocol, and allows the existence of backup path.