The principle of the switch

- Mar 27, 2018 -

The switch works on the second layer of the OSI Reference Model, the data link layer. The CPU within the switch will be successfully connected to each port, creating a Mac table by matching the MAC address to the port. In future communications, packets destined for the MAC address will be sent only to their corresponding ports, not all ports. Therefore, the switch can be used to divide the data link layer broadcast, that is, the conflict domain, but it can not divide the network layer broadcast, namely broadcast domain.

The switch has a very high bandwidth back bus and an internal exchange matrix. All the ports on the switch are hooked up on this back bus, after the control circuit receives the packet, the processing port finds the Address table in memory to determine the port on which Nic (NIC) is hooked on the destination Mac (the hardware address of the network card), and transmits the packet quickly to the destination port through the internal exchange matrix. If the Mac does not exist, broadcast to all ports, and the receiving port responds, the switch "learns" the new MAC address and adds it to the internal MAC address table. Using a switch can also "segment" The network, by comparing the IP Address table, the switch allows only the necessary network traffic through the switch. The filtering and forwarding of the switch can effectively reduce the conflict domain, but it can't divide the network layer broadcast, that is broadcast domain.


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