The switch operates at the second layer of the OSI reference model, which is the data link layer. The CPU inside the switch will form a MAC table by matching the MAC address with the port when each port is successfully connected. In future communication, packets sent to this MAC address will only be sent to its corresponding port, not all ports. Therefore, switches can be used to partition data link layer broadcasts, i.e. conflict domains; But it cannot divide the network layer broadcast, that is, the broadcast domain.
The switch has a high bandwidth back bus and internal switching matrix. All ports of the switch are connected to this back bus. After the control circuit receives the data packet, the processing port will look up the address comparison table in memory to determine which port the destination MAC (hardware address of the network card) of the NIC (network card) is connected to. The data packet is quickly transmitted to the destination port through the internal switching matrix. If the destination MAC does not exist, it is broadcasted to all ports. After the receiving port responds, the switch will "learn" the new MAC address and add it to the internal MAC address table. Switches can also be used to "segment" the network. By comparing with the IP address table, switches only allow necessary network traffic to pass through them. By filtering and forwarding through switches, conflict domains can be effectively reduced.
