The forwarding of data packets by switches is based on physical addresses (MAC addresses). For IP network protocols, it is transparent, meaning that switches do not know or need to know the IP addresses of the source and destination devices when forwarding data packets, only the destination MAC address.

During the operation of the switch, it continuously collects information to establish a MAC address table. This table is quite simple, indicating on which port a certain MAC address was discovered.

When a switch receives a TCP/IP packet, it first confirms whether it is a broadcast packet, and if so, broadcasts the packet to all ports; If not, the destination MAC will be queried in the MAC address table to confirm which port the packet should be sent from (if the destination MAC address is the same as the source MAC address, it will be considered an invalid packet and discarded).

If the destination MAC address cannot be found in the address table, the switch will forward the packet from all ports except the receiving port, just like handling broadcast packets. After the corresponding port responds, the switch will "learn" the new MAC address and add it to the MAC address table.

• The working principle of the switch
• The difference between switches and routers