Find out why the router failed

1. Router Status

Figure out what state the router is in when it fails to take the next step. The most direct way is to observe the working status of the various LEDs on the router, and if you don't know what he means, you can view the user manual. With the command line interface and the router direct dialogue to get more detailed information, common routers can use "show" or "display" to display the router's current working status and configuration information. In short, it is a basic requirement to understand the situation.

2. What should be the outcome of the normal situation

You should first make sure what you want the router to do and configure the router according to your ideas to verify what the router should be capable of. For example, should you be able to ping the address of the specified interface? A broadcast online OSPF should all the neighbors be full? After you debug the router you should be able to answer these questions correctly and confirm what you want.

3. Possible causes of some kind of error

To answer this challenging question, it is not enough to have courage, but more knowledge and experience. Regardless of that error, there may be several causes, possibly a fault or multiple fault overlays. Of course, a full and reliable enumeration of causes requires a comprehensive understanding of the situation of specific networks and devices. Your level of knowledge and experience is evident here.

4. Eliminate the illusion and find the real killer

There are a number of "reasons" for a failure, but it does not mean that all "cause" problems occur. So the elimination method is the best choice, we can sum up the following process diagram to answer it.

A qualified network engineer should be in the process of dealing with the failure of the time to ask themselves questions, and calmly to analyze, and finally put forward the plan and carefully one by one, the final release of the fault, further increase their own maintenance experience.

Router Troubleshooting theory

Single machine failure or network failure?

Single-machine failure is generally related to the physical failure of the equipment and accessories, such as the power supply problems caused the equipment to run abnormally, cable causes the router interface can not detect the normal signal. The software processing has the flaw also belongs to the single machine fault category, assumes the processing too large NAT hash table or the routing table, the memory exhaustion causes the router to be paralyzed.

Routers are the core device of network interconnection, so they have to be associated with the whole network. For example, an office network accesses the Internet via PSTN or ADSL dialing, requires the proper installation of routers and connects external cables, a simple configuration of the router, including the dialer configuration, and also requires the terminal host to specify the gateway and DNS addresses. On the other hand, more and more complex network application environment has put forward more request to the network equipment's error. Therefore, in the process of fault handling, whether for connectivity failures or performance problems, a comprehensive and systematic understanding of the network situation, a comprehensive analysis.

Physical failure of routers

Router installation and use precautions should be carried out in strict accordance with the installation manual. Before installation should check the installation site temperature and humidity, cleanliness, static electricity, interference, lightning protection requirements are met, after installation should check the power supply input voltage amplitude, frequency, neutral point of connection and protection, grounding resistance, etc. to meet the requirements.

Cannot be used after installation

* Line connection problem. such as line impedance mismatch, line sequence connection error, intermediate transmission equipment failure.

* Problem with other equipment.

* Interface configuration issues.

* Power or grounding does not meet the requirements.

* In the installation process also consider the module interface cable to support the maximum transmission length, maximum speed and other factors.

A failure occurred during use

* Power, grounding and protection do not meet the requirements, in the case of voltage drift or lightning damage caused by the device.

* Transmission lines are disturbed.

* Intermediate transmission equipment failure.

* Ambient temperature and humidity, cleanliness, static and other indicators beyond the scope of use.

In the process of fault location, unnecessary connected equipment can be removed first, and the range of fault locating is reduced, which is helpful for locating faults quickly and accurately.

A fault caused by a virus attack

After the network environment becomes complex, the virus attack has become the factor that the router error and maintenance have to consider. Viruses and illegal messages are forwarded by routers, which can take up a lot of resources from the router. If the router's CPU usage is too high, packet packet loss rate, you can disconnect the local LAN, by grasping packets and other means to determine whether there is a local attack occurred. The use of access control to filter illegal packets on routers based on these attack messages usually has a certain effect. Of course, the most fundamental solution is to completely antivirus the local computer, but the workload is also huge.

Error-Shooting engineering is a complex project, requiring administrators to have a deep knowledge base and technical level, while dealing with very complex faults requires patience, carefulness and clear logical thinking. In the process of debugging, while increasing the experience of the administrator, can provide help for the future work, so that the wrong project more efficient, more formal, the administrator can also get professional satisfaction.