What is a switch

A switch is a network device used for electrical (optical) signal forwarding. It can provide an exclusive electrical signal path for any two network nodes connected to the switch. The switch is only used to distribute network data. It can connect many hosts, each of which has its own external IP. The switch works at the relay layer, addressing based on MAC address, and cannot provide this function.

The operating environment of this tutorial: Windows 7 system, Dell G3 computer.

What is a switch

A switch is a network device used for forwarding electrical (optical) signals. It can provide an exclusive electrical signal path for any two network nodes connected to the switch. The most common switch is an Ethernet switch. Other common ones include telephone voice switches, fiber optic switches, etc.

The transmission modes of the switch include full-duplex, half-duplex, and full-duplex/half-duplex adaptive. The full duplex of the switch means that the switch can also receive data while sending data, and the two are synchronized. This is just like when we usually make a phone call, we can hear the other party's voice while talking. All current switches support full duplex. The advantage of full-duplex is small delay and high speed.

The switch is only used to distribute network data. It can connect many hosts, each of which has its own IP to the outside world. The switch works at the relay layer and is addressed based on MAC address, and cannot provide this function.

The working principle of the switch

The switch works on the second layer of the OSI reference model. It has A very high bandwidth back bus and internal switching matrix, all ports are connected to this back bus. When working, the switch will first establish the mapping between the source MAC address in the received data frame and the switch port, and write it into the MAC address table. The switch then compares the destination MAC address in the data frame with the established MAC address table to determine which port to forward. If the destination MAC address in the data frame is not in the MAC address table, it is forwarded to all ports. When a receiving port responds, the switch will learn the new MAC address and add it to the internal MAC address table, thereby "segmenting" the network. In future communications, data packets sent to this MAC address will only be sent to its corresponding port, not all ports.

The switch can transmit data between multiple port pairs at the same time. Each port can be regarded as an independent network segment. The network equipment connected to it enjoys all the bandwidth alone without sharing with other ports. Equipment competes for use. When node A sends data to node D, node B can send data to node C at the same time, and both transmissions enjoy the full bandwidth of the network and have their own virtual connections.

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