How to Flush DNS

When troubleshooting network issues or ensuring the most up-to-date version of a website is displayed, one of the most effective and often overlooked solutions is flushing the DNS cache. Whether you’re a technical writer documenting system processes or a developer fixing network issues, understanding how DNS works and how to flush the DNS cache is essential.

In this article, we’ll cover what DNS caching is, why and when you might need to flush your DNS, and how to do it across different operating systems. By the end, you’ll have a solid grasp on how flushing DNS can optimize network performance and resolve technical issues.

What is DNS?

DNS, or Domain Name System, is essentially the "phonebook" of the internet. When you type a website’s domain name (like www.example.com) into your browser, DNS translates that human-readable domain into an IP address (such as 192.0.2.1) that your computer uses to locate the website.

What is DNS Caching?

DNS caching occurs when your operating system temporarily stores DNS query results to speed up future visits to the same website. By caching DNS information, your computer doesn’t need to query DNS servers every time you visit a website, resulting in faster load times.

Why Would You Need to Flush DNS?

Over time, the DNS cache can become outdated or corrupted, leading to various problems:

• Website changes: If a website has recently migrated to a new IP address or a new server, your cached DNS information may point to the old, incorrect IP.
• Network issues: Corrupt DNS entries in the cache can cause websites to fail to load or show errors like “Page not found” or “DNS server not responding.”
• Security reasons: Flushing DNS can clear malicious DNS entries that may have been injected by malware or during a DNS spoofing attack.
• Website access issues: If a site has changed its DNS settings, you may encounter trouble accessing the website until your cache is cleared.

How to Flush DNS: A Step-by-Step Guide

Flushing your DNS cache is a straightforward process that can resolve many internet connectivity issues. The steps to flush DNS differ depending on the operating system. Below are instructions for Windows, macOS, and Linux.

Flushing DNS on Windows

1. Open Command Prompt:

   • Press the Windows key, type cmd or Command Prompt, and select it from the search results.
   • Alternatively, you can press Windows + R, type cmd, and press Enter.

2. Run the flush DNS command: In the Command Prompt window, type the following command and press Enter:

   bash

    

   ipconfig /flushdns


3. Confirmation message: After running the command, you should see the following message confirming the DNS cache has been cleared:

    Successfully flushed the DNS Resolver Cache.


Flushing DNS on macOS

1. Open Terminal:

   • Press Command + Space to open Spotlight, type Terminal, and press Enter.
   • Alternatively, go to Applications > Utilities > Terminal.

2. Run the flush DNS command: The exact command depends on your version of macOS. Below are some common commands for various versions:

   • For macOS Monterey, Big Sur, and Catalina:

      sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder


   • For macOS Sierra, High Sierra, and Mojave:

      sudo killall -HUP mDNSResponder


   • For macOS Yosemite:

      sudo discoveryutil mdnsflushcache


3. Enter your password: You’ll be prompted to enter your administrator password. Once you do, the DNS cache will be flushed, and no confirmation message will be shown.

Flushing DNS on Linux

On Linux, DNS caching isn’t always handled by the OS itself but rather by specific services like systemd-resolved or dnsmasq. Here’s how to flush DNS on some common Linux distributions.

1. For Ubuntu (with systemd-resolved):

   • Open the terminal.
   • Run the following command:
     arduino

     sudo systemd-resolve --flush-caches


2. For Linux distributions using dnsmasq:

   • Open the terminal.
   • Restart the dnsmasq service by running:
      

     sudo systemctl restart dnsmasq


3. For Linux distributions using nscd (Name Service Caching Daemon):

   • Open the terminal.
   • Run the following command:
     bash

     sudo /etc/init.d/nscd restart


Verifying the DNS Cache Flush

After flushing the DNS cache, it’s a good idea to verify that the process was successful. While most operating systems don’t display a confirmation message, you can use a few additional commands to ensure your DNS resolver is working correctly.

On Windows:

• After flushing the DNS, you can test the DNS resolution with the following command:
   

  nslookup www.example.com

  If the website resolves to the correct IP address, your DNS is functioning correctly.

On macOS and Linux:

• Use the dig command (requires installation of dnsutils on Linux):
   

  dig www.example.com

  The output should display the correct IP address of the domain, confirming that the cache has been updated.

When to Flush DNS

Knowing when to flush DNS can help you resolve potential issues faster. Here are common scenarios where flushing the DNS cache is beneficial:

• Website has recently moved: If a website has moved to a new server or IP address, flushing DNS ensures you are pointed to the correct address.
• Resolving "Page Not Found" errors: Sometimes, a corrupted cache can cause websites to fail to load.
• Frequent DNS issues: If you experience intermittent connection issues or trouble accessing certain websites, a DNS flush can resolve the problem.
• Post-malware removal: If you’ve recently removed malware from your machine, flushing the DNS cache can help clear any malicious DNS entries.

Technical Marketing Tasks

Flushing your DNS cache is a simple but powerful troubleshooting step for resolving network issues and ensuring that your system retrieves the most up-to-date DNS information. Whether you’re a technical writer documenting the process or a developer dealing with DNS issues, this essential step can prevent and resolve connectivity problems, optimize your system’s performance, and enhance security.

Make it a regular practice to flush your DNS cache when troubleshooting network issues or after making significant DNS changes to avoid slow page loads and outdated DNS records.

By understanding how to manage DNS effectively, you can help keep systems and networks running smoothly, ensuring users can access websites without any interruption.