Shulou(Shulou.com)06/01 Report--

In this issue, the editor will bring you about the operation of the working principle of the switch. The article is rich in content and analyzes and describes for you from a professional point of view. I hope you can get something after reading this article.

There are three kinds of operation in the working principle of the switch: 1, discarding, that is, discarding when the host under this port accesses the host under the known port; 2, forwarding, that is, forwarding when the host under a certain port accesses a host under a known port; 3, diffusion, that is, when a host under a certain port accesses a host under an unknown port, it will spread.

The operating environment of this tutorial: windows7 system, Dell G3 computer.

A switch is a network device for forwarding electrical (optical) signals. It can provide an exclusive electrical signal path for any two network nodes of the access switch. The most common switch is the Ethernet switch. The switch operates at the second layer of the OSI reference model, the data link layer. The switch has a high-bandwidth back bus and an internal fabric that can transfer data between multiple port pairs at the same time. The transmission modes of the switch are full-duplex, half-duplex, full-duplex / half-duplex adaptive.

working principle

Address table

The port address table records the MAC address of the host under the port. The port address table is established automatically after the switch is powered on.

Saved in RAM and maintained automatically.

The principle of a switch isolating collision domains is based on its port address table and forwarding decisions.

Forwarding decision

There are three operations in the forwarding decision of the switch: discard, forward, and spread.

Discard: discards when a host under this port accesses a known host under this port.

Forwarding: forward when a host under a port accesses a host under a known port.

Diffusion: when a host under a port accesses a host under an unknown port, it spreads.

Each operation should record the MAC address of the sending end in case of access by other hosts.

Survival period

Lifetime is the lifetime of the table item in the port address list. Each table item begins a countdown after it is established, and each time it is sent

The data should be refreshed and timed. For hosts that do not send data for a long time, the table entry of their MAC address is deleted at the end of the lifetime.

So the port address table always records the MAC address of the most active host.

(4) it should be said that the switch has a lot to learn. Here we mainly introduce the switch structure and networking mode. Since the 10s of the 21st century, the network has been used more and more widely, and the switch has played a more and more important role as a link in the network. To put it simply, the switch just connects it to the user's computer and completes the data exchange between each computer. In terms of complexity, for the position in the whole network, some high-level switches, such as layer 3 switching and network management products, are not so simple in switch structure.

Layer 3 switch

In general, ordinary switches work only at the data link layer, while routers work at the network layer. The powerful layer 3 switch can work at both the data link layer and the network layer and forward packets according to the MAC address or IP address. However, it should be noted that the layer 3 switch can not completely replace the router, because it is mainly for the communication of Vlan in two different subnets, rather than for complex path selection of data transmission.

Network management function

The degree of management supported by a switch reflects the manageability and operability of the device. The switch with network management function can monitor the traffic of each port, set the rate of each port, and close / open the port connection. Through the monitoring of the switch port, it is convenient to distinguish the network traffic and quickly define the network fault, and improve the manageability of the network.

Port aggregation

This is an encapsulation technology, it is a point-to-point link, both ends of the link can be switches, switches and routers, or hosts and switches or routers. Based on the port trunking (Trunk) function, it allows the simultaneous transmission between the switch and the switch, the switch and the router, the host and the switch or the router through two or more ports in parallel to provide higher bandwidth, greater throughput, and significantly provide the entire network capacity.

These are the operating principles of the switch shared by the editor. If you happen to have similar doubts, you might as well refer to the above analysis to understand. If you want to know more about it, you are welcome to follow the industry information channel.

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