This is what happens behind the curtain when you ask your web browser to load a website. You type in a URL like lifewire. This happens for every website you want to visit. Every time you visit a website by its hostname, the web browser initiates a request out to the internet, but this request cannot be completed until the site's name is "converted" into an IP address. The DNS cache attempts to speed up the process even more by handling the name resolution of recently visited addresses before the request is sent out to the internet.
There are actually DNS caches at every hierarchy of the "lookup" process that ultimately gets your computer to load the website. Before a browser issues its requests to the outside network, the computer intercepts each one and looks up the domain name in the DNS cache database.
The database contains a list of all recently accessed domain names and the addresses that DNS calculated for them the first time a request was made. A DNS cache becomes poisoned or polluted when unauthorized domain names or IP addresses are inserted into it. Occasionally a cache may become corrupted because of technical glitches or administrative accidents, but DNS cache poisoning is typically associated with computer viruses or other network attacks that insert invalid DNS entries into the cache.
Poisoning causes client requests to be redirected to the wrong destinations, usually malicious websites or pages full of advertisements. For example, if the docs. This poses a massive problem for popular websites. If an attacker redirects your request for Gmail. When troubleshooting cache poisoning or other internet connectivity problems, a computer administrator may wish to flush i. This is called DNS poisoning or DNS spoofing, and it can redirect you to a website designed to gather sensitive data, such as passwords to online accounts.
The first time you visit a site after clearing the cache, the site might be a little slower than usual, but after, the results will speed up again. Using a tool can help you keep track of DNS performance and identify issues before they cause a serious problem. With a tool like SolarWinds SAM installed, you may also receive an alert or notice other information prompting you to clear the cache. You should then get a message indicating the cache has been successfully flushed.
If you want to view the entries before clearing the cache, open the command prompt and type the command:. You can then review the entries and decide if you want to proceed with flushing the DNS. If the cache problem is on the server instead of the local machine, you can still use the command prompt, but with a different command.
In this case, it would be:. On the basis of the listed addresses, including additional information such as the validity period if given , you can get an approximate overview of your page history. In any case, your address storage betrays which projects you call up regularly or over a long time. The more comprehensive the collection of cached addresses is, the more you reveal yourself. Security against manipulation: You should also clear the DNS cache from time to time for security reasons.
The information in the cache is practical for delivering web projects — but can quickly become dangerous in the wrong hands. This so-called DNS poisoning or DNS spoofing is often used to access sensitive log-in data, for example, to online banking. With a DNS flush, you can also dispose of such manipulated records with minimal effort. In such cases, the domain name is probably filed in the cache with an incorrect or old IP address , which can be remedied by clearing the DNS cache. As a result, the request will once again be directed to the appropriate DNS server and not answered from the cache.
With the updated address information , the connection to the web project will once again work as planned. Enter the following command :. The flushdns command on Windows 7 can also work without the space used here before the slash. Windows 8 starts the search for the desired term right away. To clear the DNS cache, enter the following command:. Windows how to clear the DNS cache The command prompt works in the same way on Windows 10, and the procedure hardly differs from that of Windows 7 and 8: in the first step, use the search function to look for the command line application cmd.
To use DNS caching services in Linux distributions like Ubuntu and clear the cache, you need administrator rights. OS X Related products. Choose your computers operating system to see detailed instructions: Windows 10, 8 and 8. Windows From Home, tap or click the Desktop tile. Right-click the Start button the Windows logo in the lower-left. Choose Command Prompt Admin. When asked whether to allow Command Prompt to make changes to your computer, select Yes. Note: If you are asked for an administrative login, you will need to contact your system administrator.
Type "netsh winsock reset" and press Enter. Restart the computer.
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