A fault resolution method for DNS resolution of domain name _DNS server

Source: Internet
Author: User
Tags parse error dns troubleshooting nslookup nslookup command
The probability of this phenomenon is relatively large, so this article will be from the beginning of zero to teach readers some basic troubleshooting DNS troubleshooting methods.

first, what is a DNS resolution failure?

Generally speaking, as we visit the www.jb51.net,www.kanshule.com these addresses are called domain names, and it is well known that any host in the network is the IP address to identify, that is, only know the site's IP address to be able to successfully implement access operations.

However, because the IP address information is not very good memory, so the name of the domain name in the network, in the visit we need to enter this good memory of the domain name, the network will exist automatically to resolve the corresponding domain name to the IP address of the server, this is the DNS server. A machine capable of implementing DNS resolution can be either its own computer or a computer in the network, however, when DNS resolution errors, such as the resolution of a domain name to a wrong IP address, or do not know what the corresponding IP address of a domain name, we can not access the corresponding site through the domain name , this is the DNS resolution failure.

A DNS resolution failure is the biggest symptom of access to the site's corresponding IP address is not a problem, but access to his domain name will be an error.

second, how to troubleshoot DNS resolution failure:

When our computer has a DNS resolution problem, do not worry, the solution is simple.

(1) Using Nslookup to determine whether the DNS resolution is really a fault:

To fully determine whether the DNS resolution of the fault will need to be through the system with the Nslookup to solve.

Step one: Verify that your system is operating on Windows 2000 and Windows XP, and then enter command line mode by "Start-> run-> input cmd".

The second step: Enter the nslookup command and return to enter the DNS resolution query interface.

Step three: The Command Line window displays the DNS server address used by the current system, for example, the author's DNS server IP is

Fourth step: Next Enter the site you can not access the corresponding domain name. For example, the author input www.jb51.net, if not access, then DNS resolution should not be normal. We will receive a message from DNS request timed Out,timeout was 2 seconds. This means that our computer does have a DNS resolution problem.

Tip: If DNS parsing is normal, feedback back to the correct IP address, such as the author with www.jb51.net this address for query resolution, will get name:jb51.net,addresses:, of information.

(2) Query the DNS server is working properly:

At this point we will look at the number of DNS addresses used by our computer and inquire about his operation.

Step one: Verify that your system is operating on Windows 2000 and Windows XP, and then enter command line mode by "Start-> run-> input cmd".

Step Two: Enter the Ipconfig/all command to query the network parameters.

Step three: In the Ipconfig/all display information we can see a place to write DNS SERVERS, this is our DNS server address. For example, the author is and From this address can be seen as an extranet address, if the use of extranet DNS resolution error, we can replace a different DNS server address to solve the problem.

Fourth step: If the DNS server is displayed in the company's internal network address, so that your company's DNS resolution work is to the company's internal DNS server to complete, when we need to check this DNS server, Perform a nslookup operation on the DNS server to see if it resolves correctly. Resolves DNS service failures on DNS servers, and generally solves problems.

(3) To clear the DNS caching information method:

When a computer has access to a domain name, not every access requires help from the DNS server, in general, when the resolution is completed once, the resolution entry is saved in the computer's DNS cache list, if the DNS resolution changes, because the DNS cache list information has not changed, When the computer accesses the domain name, it still does not connect to the DNS server to obtain the latest resolution information, and resolves it based on the cached correspondence that is saved on its own computer, which can cause a DNS resolution failure. At this point we should resolve the failure by clearing the DNS cache commands.

The first step: Through the "Start-> run-> input cmd" into the command line mode.

Step two: In the command line mode we can see a parameter named/flushdns in ipconfig/?, which is the command to clear the DNS cache information.

Step three: Execute the IPCONFIG/FLUSHDNS command, indicating that the cached information for the current computer has been successfully purged when the "successfully flushed the DNS resolver cache" prompt appears.

Fourth step: The next time we visit the domain name, we will go to the DNS server to obtain the most recent resolution address, no longer because the previous cache caused a parse error failure.

(4) Modify the Hosts file law:

The modification of the hosts method is to modify the corresponding relationship of DNS in the Hosts file so as to realize the correct resolution. Because the local computer accesses a domain name, it first looks at the hosts file in the local system, and the resolution relationship in the Hosts file is greater than the resolution relationship on the DNS server.

So when we want to bind a domain name to an IP address, we can do so by adding a resolution entry in the Hosts file.

Step one: Start-> search, and then look for files called hosts.

Step two: Of course, the reader who already knows his path can go directly to the C:\windows\ System32\Drivers\Etc directory to find the Hosts file. If your system is Windows 2000, you should look for it in the C:\WINNT\SYSTEM32\DRIVERS\ETC directory.

Step three: Double-click the Hosts file and choose to open it with the Notepad program.

Fourth step: We will then see all the contents of the Hosts file, by default only one line of content " localhost". (Other lines preceded with # are not real content, just help information)

Fifth step: You want to do DNS resolution of the entries added to the Hosts file, the specific format is to write the domain name corresponding to the IP address, and then the space to receive domain name information. For example, the author added " www.jb51.net" and " www.jb51.net" two entries.

The sixth step: after setting up our visit to Www.jb51.net will automatically be based on the intranet or outside the network to resolve.

Third, Summary:

With the four steps described above, we can solve most of the DNS resolution problems, the first three of these methods are step-by-Step troubleshooting DNS resolution failures, and the last one to modify the Hosts file is in really no way, a stopgap. Of course, either way, we can solve the network failure caused by DNS resolution errors. It is believed that these methods can help jb51 readers to solve more practical problems.

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