How does a switch work?

The working principle of the switch is based on the second layer of the OSI reference model, which is the data link layer. A switch is a network device based on a learning process that enables communication between different devices in the network by parsing and forwarding data frames. The switch can continuously improve the contents of its internal forwarding table, improve the efficiency and reliability of data exchange, and ensure the stability and security of the connection. Switches are widely used in enterprise networks, data centers, campus networks and other scenarios to provide stable and efficient connection services for various applications.

The working principle of the switch is based on the second layer of the OSI reference model, which is the data link layer. The switch can provide an exclusive electrical signal path for any two network nodes connected to the switch. The switch forwards data frames according to the MAC address table, which records the corresponding information between all MAC addresses in the network and each port of the switch. When the switch receives data, it checks its destination MAC address and then forwards the data out the interface where the destination host is located.

The switch has a learning function. It checks the source MAC address in the data frame to establish the mapping between the address and the switch port, and writes it into the MAC address table. The switch 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. This process is called flooding.

In addition, the switch also has the function of isolating conflict domains. In Ethernet, each device has a unique MAC address and can send multiple data frames. The switch decides what to do with the received data frame based on its port address table and forwarding decisions. When the destination MAC address of the data frame is not in the MAC address table, the switch will flood the data frame to all ports, which helps discover new devices and establish connections.

There are significant differences between switches and routers in many aspects:

1. Working level: The switch works at the data link layer of the OSI/RM open architecture, which is the second layer. The router was designed from the beginning to work at the network layer of the OSI model, which is the third layer. Since the switch works at the data link layer, its working principle is relatively simple, and the router can make more intelligent forwarding decisions.

2. The object on which data is forwarded: The switch uses the physical address or MAC address to determine the destination address of the forwarded data. The router uses the ID numbers (i.e. IP addresses) of different networks to determine the address for data forwarding.

3. Routing function: The router has the function of automatically identifying the sending and arriving addresses of data packets. It is similar to a policeman on the road, responsible for traffic guidance and routing. In contrast, the switch only divides the collision domain, not the broadcast domain, and does not have a routing function.

4. Performance: Routers can handle the TCP/IP protocol, but switches cannot. The router can automatically identify the address where the data packet is sent and arrived. The router is equivalent to the police on the road, responsible for traffic guidance and guidance. The router only forwards data packets with specific addresses and does not transmit data packets that do not support routing protocols and data packets with unknown destination networks, thereby preventing broadcast storms.

In short, a switch is a network device based on a learning process. It realizes communication between different devices in the network by parsing and forwarding data frames. The switch can continuously improve the contents of its internal forwarding table, improve the efficiency and reliability of data exchange, and ensure the stability and security of the connection. Switches are widely used in enterprise networks, data centers, campus networks and other scenarios to provide stable and efficient connection services for various applications.

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