For those who don’t know, DNS cache or DNS resolver is a local database, which is controlled and maintained by the operating system of a computer. Most of the operating systems such as Windows, Ubuntu Linux, Mac, etc. maintain this temporary database. Usually, this temporary database keeps the record of recently visited and recently attempted internet domains. In the simplest words, DNS cache keeps the record of the recent DNS lookups.

The operating system automatically caches IP addresses and DNS results so that subsequent requests can be made fast to the same hostname. However, in this process, bad results get cached automatically sometimes that can cause improper communication with the host. Over the period, it can also give birth to numerous internet connectivity and security issues and make your DNS cache poisonous. If it is something bothering you, you should take quick steps to flush your DNS immediately.

But before proceeding, you must understand when is the right time to flush DNS. In this post, we will take a look at few points disclosing why and when you should flush your DNS.  But before that let’s understand what is the DNS cache poisoning in brief.

DNS Cache Poisoning:

You probably don’t know, but your DNS cache system may become polluted by unauthorized domain names of IP addresses. It is called DNS cache poisoning. Sometimes technical glitches and administrative accidents can be responsible for the corrupt of the cache system. However, in most cases, cache poisoning is associated with invalid DNS entries in the cache, Malware and other virus attacks, and network attacks.

Sometimes, cache poisoning can be accountable for redirecting the client request to the wrong destinations.

Why It is Needed to Flush DNS

Security –


Security should be one of the top reasons you should consider flushing out your DNS. As you can notice, DNS has been identified as a critical component you should not take it back seat.

Anyone who has access to your computer system can look at your cache and find which sites you have recently visited. By using the windows command prompt and entering ‘IPConfig,’ anyone can look at each and every entry in your cache.

The situation may become worse if someone is able to temper the DNS information in a cache. So, if you suspect any DNS-related concern, flush out your DNS records to keep your system safe and secure.

Once you have cleared out your DNS cache, it will be entirely clear except for things which are updating automatically like email clients, anti-virus, etc.

Helps in Eliminating Bad Connections –

As said in the beginning, sometimes, bad results get cashed into your DNS cache. These bad results or bad connections get bundled with a good connection because there is no provision for a separate listing for bad IP responses.

Unfortunately, if for some reason, you have the bad IP address in your cache, flushing out DNS cache is the only solution for you. Sometimes, bad IP connections contain the virus and other Malware. Therefore, it should be a good option to clear bad connections.

It can Help you Improve System & Application Performance –

Excessive cache data may slow down your system because of the RAM and memory it requires to process the data. As we mentioned in the above section, most of the time, DNS cache is filled with useless information that probably will not be accessed by you in the future you should flash your data. After clearing DNS cache, you will notice the benefit in the speed and performance of your system.

Circumstance When Flushing DNS Can be Wise Decision

In the above section, we talked about why it is necessary to flush DNS. Now we will talk about some circumstance, in which clearing DNS cache can prove a wise decision for you.

Server Migration –

Server Migration

For a webmaster, clearing the DNS cache can be quite useful while server migration. Changes to DNS server can be made immediately, but changes to the cache can take up to 48 hours. It will leave your users in a situation where they will visit a website, which is no longer available at its old IP address.

However, when you choose to flush the DNS server cache, the server is forced to discover the new IP for the domain name. This way, DNS server don’t rely on the cached addresses. It helps web owners to get immediate access to the accurate IP address quickly. If you are running a website that receives more traffic from the repeated visitors, then you must consider clearing the cache during the server migration.

Disabling DNS for Single Internet Session

You may also choose to disable DNS cache for single internet session so that cache is unable to record any DNS information until your computer system is restarted.

Maintenance –

You can consider cleaning up cache as a reasonable maintenance practice. Although the data of DNS cache does not take much space yet the list of its data can go very large. If the list is filled up with sites that you no longer visit, there will be no space for new entries.

Moreover, cleaning the cache can also help you prevent returning of the bad results and 404 errors.

Delete Old DNS Data:

There are more than 1 DNS providers available. For example, the popular search engine Google offers a DNS cache and resolution service. An another DNS option is Open ‘DNS’. Even if you have replaced your DNS, if your cache preserves the memory of your frequently visited sites from you old DNS, the browser will pull from the cache – not from the new DNS. However, if you clear the cache, you will start pulling from your new DNS.  We have cleared this point in the ‘Server Migration’  point as well.

Final Words:

All in all, we can say, flushing a DNS cache can help us resolve myriad of issues. In this post, we tried to make you familiar with circumstances in which flushing DNS can be a good decision.

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