Uncover the mystery of frequent disconnection of LAN routers

LAN routers are quite common, So I studied the frequent disconnection problem of LAN routers. I would like to share it with you here and hope it will be useful to you. Several companies in the unit building have their own LAN, and each lan has more than 30 workstations.

In the days when the network was just established, almost every workstation in the LAN router could access the Internet normally. However, it was not a long time. In a few days, a slightly larger company reflected the recent Internet access, it is often a strange phenomenon that some workstations in the same LAN can access the Internet, and some workstations cannot access the Internet. The most obvious thing is that, when multiple workstations copy and transfer files from the server system at the same time, some workstations can transmit files normally, while some workstations may lose lines during transmission, in any case, the shared resources in the server system are not accessible. Once a workstation experiences disconnection, a very simple web page cannot be opened. The original thought that this phenomenon was the existence of a company, who once thought that it was not long before, and another company reflected the same fault phenomenon, it seems that this phenomenon was not accidental.

Troubleshooting

A fault is a command. After receiving a call for assistance, I immediately went to several fault sites to perform a careful inspection and found that the time for the establishment of these LAN networks was almost the same, and the topology of each LAN was the same, both normal workstations are connected to L2 switches. l2 switches are connected to LAN routers through physical cables, while the egress light cables are directly connected to routers through the photoelectric conversion module. If the LAN with the same network topology has the same fault, it is certainly not accidental. The reason for this phenomenon is the same for different LAN routers.

At first, I thought most of this phenomenon was caused by the looseness of the physical cable connection or the damage to the connection port. Therefore, I carefully checked the LAN of one of the organizations, re-unplug each connection port and re-insert the physical cable to the corresponding port of the switch according to the correct method. However, this method cannot eliminate the fault. Considering that some workstations can access the Internet and some workstations cannot access the Internet, I try to use an alternative method to connect a workstation that cannot access the Internet to a switch port that can access the Internet, however, such an effort is still ineffective. In order to check whether there is a problem with the switch or the physical cable connection, the author tries to use the ping command to test the connectivity of other workstations in a workstation that cannot access the Internet, the result shows that all workstations in the LAN can be pinged normally, which indicates that the physical connection between the faulty workstation and the switch is normal. Later, I tried to access the shared files in other workstations through the network neighbor window, and the access result was quite smooth. This shows that the common L2 switches in the LAN router work normally. Considering that each workstation in the LAN can be normally connected, and the transfer speed of shared files between each workstation is normal, for this reason, I initially ruled out that the problem does not occur on the L2 Switch of the LAN, and the problem may occur on the LAN router.

As a result, I began to look into the LAN router. When I check the router equipment, I first routinely check whether the physical connection between the switch and the router is normal. With the help of professional tools, I found that the connection between the vswitch and the vro is normal. Later, I logged on to the vro background management interface as a system administrator and checked the parameters one by one, no suspicious information was found. Will it be that the router has been running for a long time, resulting in a fault similar to the memory error, because many network devices are prone to this type of fault in my impression; with this in mind, I immediately restarted the router system. After the system was restarted and stabilized, I found that some workstations in the LAN could not access the Internet immediately. It was originally thought that such a fault had been ruled out successfully, but it was not long before that the same fault occurred again in the LAN. It seems that this fault was not caused by a router memory error; however, I am certain that, since restarting the router system can temporarily remove the LAN router fault, at least it indicates that the LAN router is partly responsible.

Troubleshooting

After confirming that the LAN router has some responsibilities, I will immediately take a spare high-end router from my own organization to replace the faulty router device. After the replacement operation is completed, the author conducted an Internet connection test in the LAN router of this Organization. The test result shows that the faulty workstation cannot access the Internet immediately, the same fault has not occurred for a long time, which indicates that the LAN workstation is dropped without reason by the router.

In-depth fault investigation

When I replaced the old router in the LAN, I accidentally touched the shell of the router by hand and found that the surface temperature is very high. Obviously, the heat dissipation performance of this router is not very good, after the vro has been running for a long time, its working status becomes unstable. In the end, it is easy to cause a disconnection when the workstation in the LAN accesses the Internet for no reason. Later, after further understanding, the original companies in order to save the cost of networking, the selected router equipment are some cheap, low performance products. As LAN router workstations continue to access the Internet for a long time, the performance of the routers in the LAN will become increasingly unstable, and eventually lead to many strange faults in the LAN. After figuring out the cause of the failure, I suggest these companies to buy a high-grade router immediately, so that the LAN can always run stably.