What is a switch and how does it work?

Switch: Signaling device.

1. Provide network interface.

The most important application of a switch in a network is to provide network interfaces to all network devices.

The interconnection must be achieved with the help of switches. These include:

1) Connect switches, routers, firewalls, and wireless access points.

and other network devices.

2) Connect to computer devices such as computers and servers.

3) Connect to a network printer and webcam.

IP** and other network terminals.

2. Expand the network interface.

Although some switches have a large number of ports (such as 48 ports), when the network is large, the number of network interfaces that a switch can provide is often insufficient. In this case, two or more switches must be connected together to multiply the network interface.

3. Expand the network range.

Switches and computers or other network devices are connected together by transmission media, and the transmission distance of each transmission medium is limited, and the transmission distance of the same transmission medium is also different according to different network technologies. When the network coverage is large, it must be relayed with the help of switches to extend the network transmission distance exponentially and increase the network coverage.

The switch uses an address mapping table to exchange data information.

The switch operates at the second layer of the OSI reference model, which is the data link layer. When the CPU inside the switch is successfully connected, it maps the MAC address to the port to form a MAC table.

In future communications, packets destined for this MAC address will only be sent to its corresponding port, not to all ports. Therefore, the switch can be used to divide the data link layer broadcast of several books, i.e., the collision domain; But it can't divide the network layer broadcast, i.e., the broadcast domain.

The switch has a very high-bandwidth back bus and an internal fabric. All ports of the switch are attached to this back bus, and when the control circuit receives the packet, the processing port looks up the address comparison table in memory to determine which port the NIC (network card) of the destination MAC (hardware address of the network card) is attached to.

The packet is quickly delivered through the internal fabric to the destination port, and if the destination MAC does not exist, it is broadcast to all ports, and the receiving port responds and the switch "learns" the new MAC address and adds it to the internal MAC address table.