A detailed description of the intermittent fault network in broadband routing

Many users who use routers have encountered a broadband router failure problem, so I studied the broadband router failure in the intermittent network of detailed instructions, here to share with you, hope for everyone useful. No matter how large a LAN network, it is unavoidable to encounter this or that kind of strange network fault.

One of the most trouble for the unit network administrator is the intermittent interruption of Internet access, after all, with the continuous development of network technology and gradually mature, many units of staff, especially those engaged in network services units have been almost a moment can not leave the network. If the connection between the unit LAN and Internet network is frequently interrupted, then the staff of many units will basically not be able to work normally. Recently, the author of the local area network has suffered such a strange break network fault, now the author will deal with the network broadband router fault detailed process contribution to share, I hope you can be a little inspiration!

Broadband router failover

The author unit is located in the LAN network size is not very large, all workstations add up to not more than 30 units, these workstations are all connected to the two-tier switch, broadband routers through the twisted pair and two-layer switch uplink port directly connected, The ADSL dial-up Internet connection is directly connected with the external WAN port of the broadband router, and all workstations in the local area network access the Internet network through this ADSL line.

Recently the author unit responsible for LAN maintenance and management of the staff suddenly left the job, just took over the work of the new colleagues may not be familiar with the environment or other reasons, one into the job in a very short period of time encountered a lot of network failures, In particular, one of the broadband router faults made him headache. The specific phenomenon of the broadband router failure is expressed as a drop-off phenomenon occurs almost every three hours when the unit LAN is connected to the Internet. After a few minutes, the LAN is able to automatically regain access to the Internet, although there are only a few minutes to the end of the line, but given that many of the units in the office are done online , and the municipal government directly connected to the E-government system is also a high level of network connectivity requirements, even if the network connection occurs occasionally disconnect phenomenon, will obviously affect e-government and other work of normal development. The author of this new colleague of the local area network in a detailed inspection of all workstation systems, found that all workstation system running all normal, and no network virus attacks, and all workstation systems in the LAN has successfully enabled Windows Update Service, This ensures that all system security patches are installed in a timely manner, and that when testing the ports and connectivity of all network-attached cables, new colleagues do not find any physical faults.

Broadband Router Troubleshooting

Under the helpless, the new colleague in time to send a "help" to the author, listening to the new colleagues on the network fault detailed description, the author immediately according to his description of the detailed analysis, And in time to reach the three point of conclusion: The 1th is the LAN network has fallen off the phenomenon, the 2nd is that the network off the line phenomenon belongs to intermittent sexual behavior, the 3rd is the network off line failure occurs in a very short period of time can automatically return to normal.

From the previous experience, I think the network if the frequent drop line, there may be two reasons, one reason is that the network line itself is connected to instability, another aspect of the reason is that the local area network may exist worm virus, The worm may be the cause of the network's frequent failure of broadband routers. Because the author unit of the local area network is to share the Internet through the ADSL equipment, the author immediately contacted the local telecommunications department, I implore them to be able to the unit of ADSL dial-up Internet access line to check, the result they replied that there is no problem, the unit's ADSL dial-up Internet line all normal, so the author ruled out the network line of their own connection instability factors, and the focus of the fault resolution on the network worm virus; Because when the LAN environment in the worm packet is very much, it is likely to cause the broadband router device "suspended animation" phenomenon, As a result, the associated network port may be shut down, which may lead to a broadband router failure, and when the network worm virus does not attack, the closed network interface will automatically open, so that the network dropped the phenomenon after a period of time can be automatically restored.

Now that the author has decided that intermittent network router failure is caused by the worm virus, then I am ready to start seriously to remove the local area network is really a virus. As you know, the current network of many worms, especially the ARP type of network spoofing virus, they are very fast propagation speed, and very destructive, as long as any workstation in the LAN is ARP type of network spoofing virus infection, Then the network connection operation of all workstations in the LAN will be affected obviously. According to this analysis, the author of the local area network of all colleagues to use the workstation system again checked again, did not find any suspicious problems. Moreover, when network drop phenomenon occurs in LAN, the author inquires the ARP cache table of the local network through the "arp-a" string command, and finds that the Gateway MAC address information in the cached table is consistent with the LAN in normal Internet state. This result indicates that the LAN-routed broadband router failure is not caused by ARP virus spoofing