Chain problems caused by vswitch performance decline

The switch performance is still quite common, So I studied the chain problems caused by the decline in the switch performance. Here I will share it with you, hoping it will be useful to you. One of the following network faults in this article is the failure to withstand the LAN broadcast storm due to poor switch performance, and the cache overflow error, which eventually leads to the failure of the LAN to access the Internet! Considering that the fault occurrence rate is not high, it is easy to take a detour to solve the problem. For this reason, I have restored the detailed troubleshooting of the fault and communicated with you!

Some computers cannot connect to the Internet

The local area network of a certain organization is not very large. A total of about 40 ordinary computers are connected to two L2 switches with the same brand and model respectively, the two L2 switches are connected to the core switch of the Organization through the cascade method. At the same time, the two file servers are also directly connected to the core switch, and the core switch is directly connected to the Internet.

In normal times, every common computer in the LAN can access the file server of the organization, and can also directly access the Internet through the LAN, computers connected to two different L2 switches can also share access with each other. For a long period of time, all switches in the LAN can work normally. However, recently, several users in the LAN want to share communication files through the network, nor can they find the other party's shared resources from the Internet neighbor window, so they have to seek help from the author. At first, the author thought this was just an individual phenomenon, but it didn't take long, some other friends called to say that the Network could not be accessed. At this time, the author realized that there may be a major problem in the LAN network.

The author randomly came to a site of a common computer that could not access the Internet and checked the details of the computer, the results show that the computer's Internet parameters are correctly set, the network interface is secure, and the system runs normally. Then, I checked several computers, it was found that some computers could access the content on the Internet, and the network access speed was still very fast. After carefully comparing the details of Internet access and computer access failure, I couldn't find any suspicious places. Why?

Troubleshooting

Since there are multiple common computers in the LAN that cannot access the Internet, will it be a problem with the core network equipment in the lan? With this in mind, I immediately went to the LAN's main data center and checked the switch devices in the wiring cabinet. I accidentally found that one of the two-layer switches was obviously abnormal (2 ), because all the signal lights in the control panel of the switch are in the light but not blinking state, and the signal lights remain unchanged, it means that no data signals in the network are being exchanged for transmission. After further checks and tests, I found that all computers connected to the faulty vswitch cannot access the Internet, while all the computers connected to the other L2 Switch can access the Internet normally.

Is there a hardware fault for the long bright and non-blinking switch? To verify whether the faulty switch has hardware damage, I first unplugged the power cable connecting to the switch and re-inserted the power cable several minutes later, after the faulty switch is restarted, all the signal lights in the corresponding control panel are restored to a normal blinking State. At this time, when I attempt to access the Internet from the faulty computer, the network connection is also normal, and the network connection speed is also in one breath. I did not dream of simply restarting the faulty switch device. It seems that a very complex network fault was solved instantly. However, it was not a long time. One hour after the faulty switch device was restarted, all the signal lights on the control panel become bright and non-blinking. computers that can access the network cannot access the Internet normally, at this time, the core switch of the Unit and the other layer-2 switch work normally. Why?

Investigate Fault Causes in Depth

The Faulty Switch can work normally for a period of time after it is restarted. This indicates that the switch has not been damaged by hardware. It seems that the problem still lies in the "soft" setting, is it possible that the Internet virus is secretly "working? I think that some time ago, the LAN once experienced slow Internet access due to a network virus attack. Later, I asked each person to manually scan and kill the virus, however, I believe there must be viruses in the LAN. Will these residual Network Viruses cause abnormal switch performance? But in another thought, if the network virus is "doing something" in the dark, then the two L2 switches in the LAN should all be faulty. After all, they have the same brand and model, even the connection methods are the same, but now only one layer-2 switch is faulty, so I believe that The Faulty Switch still has a hardware fault. To solve the problem that some computers cannot access the Internet, the only way is to replace the switch device.

However, since no slave switch can be used by the organization, I had to first turn off the power of the Second-layer switch. After a period of time, I would like to reflect the situation and purchase a new switch. While these general computers cannot access the network, the author decided to manually complete Anti-Virus for all computers connected to the faulty switch, in order to completely eliminate all the factors that threaten the stability of the LAN. After several days of anti-virus, I can see that many popular viruses are hidden in the LAN. When I search for details about a virus on the internet, it is found that this type of network virus is prone to broadcast storms. Is it possible that the broadcast storm caused by the network virus causes the abnormal operation of the Layer 2 switch? Because all viruses in the LAN are cleared, it is reasonable to say that there should be no broadcast storms in the LAN at this time, so will the status of the Second-layer switch be able to recover to normal? In order to check whether my guess is correct, I re-connected the power of the Second-layer switch. At first, the switch was working normally, however, I still worry that the switch will encounter the same fault in an hour. However, it turns out that my worries are redundant. After several hours in a row, all the indicators in the control panel of the Second-layer switch are still in the flickering State. At this time, the author vaguely felt that the switch would not be faulty. Indeed, after several consecutive days of operation, some computers that had previously been unable to access the Internet have never been dropped, which indicates that the above network faults have been successfully solved.

Uncover the riddle of switch Paralysis

Although some computers cannot access the Internet, the failure has been solved, but why is one of the two-layer switches paralyzed is still confusing for me, because in the LAN, since there is a broadcast storm, why is another L2 Switch with the same brand, model, and connection method not affected? With such questions, I went to the Internet to ask some network experts. After repeated communication and analysis with the network experts, I finally found the real cause of switch paralysis: network viruses are the surface cause of some computers being unable to access the Internet. Because of Network viruses, a broadcast storm occurs in the LAN, which causes an abnormal status of a layer-2 switch, therefore, all computers connected to the faulty vswitch cannot access the Internet. In fact, the performance of the paralyzed L2 Switch is the real cause of network failure, although the models, brands, and connection modes of the two L2 switches in the LAN are the same, the duration of their operation may be different, and the degree of aging of the switch's performance components may also be different, the layer-2 switch, which has a severe aging performance, cannot withstand the broadcast storm and eventually leads to a cache overflow error. When I clear all the viruses in the LAN, then the broadcast storm will not attack the faulty switch. This is also the reason why the working status of the faulty switch system can be restored after the faulty switch system is restarted.

Final fault Summary

From the above troubleshooting process, we think that the performance of the switch is very important to the stability of the LAN's overall performance! In order to make the lan network run more stably, when we build a LAN, we cannot blindly look at the product price and choose some low-price switches with poor quality and low memory capacity, instead, we should choose switch devices with reliable quality, excellent brands, and large memory capacity. After all, such high-end devices have strong anti-interference capabilities.

To prevent frequent broadcast storms in the LAN, we should install professional firewall programs in the LAN and install anti-virus software on each computer, at the same time, the virus database program is updated online in a timely manner to clear the virus. Of course, in addition to network viruses that can cause broadcast storms, connection loops caused by network connection errors and hardware damage to network devices can also cause broadcast storms, therefore, if broadcast storms still exist in the LAN after network viruses are detected, we should carefully check whether network loops exist in the LAN, or check whether the network device is damaged by hardware.