What is DNS cache? How to clear it to solve DNS server not responding problem?

When you visit a website, your computer needs to find the associated IP address of that website. This is where DNS (Domain Name System) comes into play, converting human-readable domain names into machine-readable IP addresses. However, for efficiency and speed, your computer stores this information in a local database known as the DNS cache. While the cache is designed to speed up future requests, sometimes it can become outdated or corrupted, causing issues like the "DNS server not responding" error. In this article, we will discuss what DNS cache is, why it may cause problems, and how to clear it to resolve common DNS-related issues.

What is DNS Cache?

DNS cache is a temporary storage on your computer or network device that stores DNS records for websites you have visited. These records include the IP addresses of domain names you’ve accessed, which helps speed up the browsing process. The cache allows your computer to avoid querying the DNS server every time you visit a website, reducing load times. However, just like any cache, DNS cache can become outdated or corrupted over time.

Every time you type a website address into your browser, your computer or device first checks the local DNS cache to see if it has the corresponding IP address. If the IP address is found, your computer can quickly connect to the site without needing to contact the DNS server. However, if the cached information is outdated, it may cause connection issues or errors, such as "DNS server not responding."

Why Do You Encounter the DNS Server Not Responding Issue?

The "DNS server not responding" error typically occurs when your computer or device is unable to reach the DNS server to resolve a domain name into an IP address. This can be caused by various factors, including:

1. Outdated DNS Cache: When your DNS cache contains incorrect or expired records, your device may fail to connect to websites.

2. Corrupted Cache: Sometimes, the cache itself can get corrupted, causing connection issues even if the information stored in it is still technically valid.

3. DNS Server Issues: The problem might also lie with the DNS server itself, which could be down or malfunctioning.

4. Internet Connection Problems: A poor or unstable internet connection may prevent your computer from accessing the DNS server.

5. Firewall or Security Software: Some security software or firewalls might block access to DNS servers, resulting in the error.

By clearing the DNS cache, many of these issues can be resolved, restoring your ability to access websites and connect to the internet.

How to Clear DNS Cache to Solve the Issue?

Clearing your DNS cache is a relatively simple process and can often resolve connection issues related to outdated or corrupted DNS information. Below are the steps to clear the DNS cache for different operating systems.

For Windows Users

1. Open the Command Prompt: Press the `Windows` key, type "cmd," and press `Enter`. Make sure to run it as an administrator by right-clicking on it and selecting "Run as administrator."

2. Run the Flush DNS Command: In the Command Prompt window, type the following command:

```

ipconfig /flushdns

```

Press `Enter`.

3. Confirmation: After running the command, you should see a message that says: "Successfully flushed the DNS Resolver Cache." This indicates that your DNS cache has been cleared successfully.

4. Restart Your Browser: After clearing the cache, restart your web browser and check if the "DNS server not responding" error is resolved.

For macOS Users

1. Open Terminal: Go to `Applications` > `Utilities` and open the Terminal application.

2. Run the Flush DNS Command: Depending on your macOS version, enter one of the following commands and press `Enter`:

- For macOS High Sierra or later:

```

sudo killall -HUP mDNSResponder

```

- For macOS Yosemite to El Capitan:

```

sudo discoveryutil mdnsflushcache

```

3. Enter Your Password: You may be prompted to enter your administrator password to execute the command.

4. Restart Your Browser: After the cache is cleared, restart your browser to see if the error is resolved.

For Linux Users

1. Open Terminal: Access the terminal from your application menu or by using the `Ctrl+Alt+T` shortcut.

2. Run the Flush DNS Command: In the terminal, type the following command and press `Enter`:

```

sudo systemd-resolve --flush-caches

```

3. Confirmation: You won’t receive any output if the command is successful, but the DNS cache should now be cleared.

4. Restart Your Browser: Restart your browser and check if the issue has been resolved.

For Routers

If the DNS issue is not limited to your device and affects your entire network, the problem might be with your router's DNS cache. Clearing the router’s cache can help resolve the problem.

1. Log into Your Router: Open a web browser and enter the router’s IP address in the address bar (usually something like `192.168.0.1` or `192.168.1.1`).

2. Access the Router Settings: Enter your login credentials to access the router’s settings.

3. Locate the DNS Settings: Depending on your router, the DNS settings may be under categories like "Network," "WAN," or "LAN."

4. Clear DNS Cache: Look for an option to clear the DNS cache or restart the router. After clearing the cache, restart your router and check if the error is resolved.

Additional Tips for Fixing DNS Server Not Responding Issue

If clearing the DNS cache does not resolve the issue, there are additional troubleshooting steps you can take:

1. Change DNS Servers: Sometimes, the DNS server you are using may be unreliable or slow. Switching to a different DNS server, such as Google's DNS or Cloudflare’s DNS, can improve your connection.

2. Check Your Firewall: Ensure that your firewall is not blocking access to DNS servers. You may need to adjust your firewall settings or temporarily disable it to test the connection.

3. Reset TCP/IP Stack: On Windows, you can reset your TCP/IP stack to ensure that network configurations are set correctly. Open Command Prompt as administrator and run:

```

netsh int ip reset

```

4. Restart Your Modem or Router: Power cycle your modem or router to reset the connection and clear any temporary network issues.

5. Contact Your ISP: If none of the above methods work, there may be an issue with your Internet Service Provider’s DNS servers. Contact them for assistance.

DNS cache plays a crucial role in speeding up your browsing experience by storing DNS records. However, when the cache becomes outdated or corrupted, it can lead to errors such as the "DNS server not responding" issue. By following the steps outlined above to clear your DNS cache, you can resolve these issues and restore your internet connectivity. If the problem persists, additional troubleshooting steps, such as changing DNS servers or checking your firewall, may be necessary.