Loopback Test and Processing Methods of Industrial Switch

According to the statistical report on the development of the Internet in China, the number of netizens in my country has reached 940 million, and the Internet penetration rate has reached 67.0%.With the rapid development of the chip manufacturing process, the single-port service carrying capacity and operation stability of Industrial Switches have been continuously improved, which not only ensures excellent network performance, but also has good economics.

However, physical loops often occur in the existing network due to operational reasons such as the access of new industrial switches, the opening of new services, and network adjustment and optimization.Once a physical loop occurs in the network, triggered by ARP update packets, broadcast packets will circulate continuously after passing through the loop, resulting in broadcast storms.Although the virtual local area network VLAN (Virtual LAN) technology is used, it can be realized that the industrial switch does not transmit broadcast information to network devices other than the virtual local area network, so that the network will not be degraded due to broadcast storms.However, if the anti-loop configuration of the industrial switch is not standardized, the broadcast traffic will be transmitted to the entire upper-layer network, which will eventually consume the CPU resources of the affected network devices, resulting in frequent network protocol ups and downs, and the most serious consequence will lead to the paralysis of the entire network.

When an industrial switch fails, how should we perform quick detection based on the port number of the industrial switch? Is the configuration correct?Today we will introduce a method - loopback test!

What is Industrial Switch Loopback Testing

A loopback test is a test method that is usually used to detect and resolve port number or route problems.It is based on the process of returning (looping back) the information from the communication device to the original place to determine whether the device is operating normally or to confirm the specific location of the failed node in the network.

When it can be preliminarily judged to be a route problem according to the fault condition, it is usually carried out from one end of the device, looped back from the nearest node to this device, and gradually expanded to a node at a further level and a node at a further level. It is used for different times. The nodes loop back to the same device to distinguish which two nodes have problems with each other. This method is called segmented loopback test.

How to debug the port number of an industrial switch

1. Simplex loopback test

①Embed a duplex fiber optic module in the industrial switch.

②Use a network fiber loopback module or a simplex fiber pigtail to connect the sending end and the receiving end of a fiber optic module in a loop to check whether the port number of the industrial switch and the main parameters of the fiber optic module are normal.

③ Check the main parameters and carry out adjustment.

2. Duplex loopback test

①Embed two duplex fiber optic modules in the industrial switch.

②Then use two network optical fiber loopback modules or a duplex optical fiber pigtail to connect the two optical fiber modules in a loop, and check whether the transmission rate of the optical fiber module matches the operating speed of the switch port number, and whether the connection is normal.

③ Check the main parameters and carry out adjustment.

Conclusion: According to the loopback test is the most cost-effective and effective way to verify the configuration of industrial switches.

After the industrial switch detects a loop on the port, the required processing method is shutdown-port to realize anti-loop protection. There are four processing methods, namely:

shutdown-port #When a loop occurs, shut down the port

shutdown-svi #When a loop occurs, close svi, svi is the ip interface that contacts vlan, one svi can only be connected to one vlan

warning #When a loop occurs, display a warning message

block #When a loop occurs, change the state of the port to block blocking state