The main function of the switch, including physical addressing, network topology, error checking, frame sequence and flow control. Currently, the switch also has some new features such as VLAN (Virtual LAN) support, link aggregation support, and even some also have firewall capabilities.

In addition to the switch of the same type of network connection, it can also play a role in the interconnection between different types of networks (such as Ethernet and Fast Ethernet). Today, many switches can support Fast Ethernet or FDDI and other high-speed connection port for connecting to other network switches or to provide additional bandwidth for the large bandwidth of critical servers.

In general, each port of the switch are used to connect a separate network segment, but sometimes in order to provide faster access speeds, we can put some important network computers directly connected to the switch port. Thus, the key server and key users of the network will have faster access speeds, support for greater information flow.

Learning Function: Ethernet switch port connected to know each device's MAC address, and the address together with the corresponding port mapping is stored in the cache of the switch MAC address table.

Forwarding Filter: When the destination address of a data frame in the MAC address table in the mapping, it is forwarded to the port connected to the destination node instead of all ports (if the frame is a broadcast / multicast frames are forwarded to all ports).

Cancellation loop: When the switch includes a redundant circuit, the Ethernet switch produced by the spanning tree protocol to avoid loops, while allowing the presence of a backup path.

Training: Ethernet port is connected to the AC machine savor each device's MAC address, and the address in response to the same port mapping is stored up in the exchange of local cache of MAC address table.

Forwarding / Filtering: When the destination address of a data frame in the MAC address table in the mapping, it is forwarded to the destination node adjacent to the port instead of all ports (if the frame is a broadcast / multicast frames are forwarded to all ports) .