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如何刷新DNS缓存

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在这篇文章中，我们解释刷新 DNS 缓存以解决公共 DNS 问题的方式。 You can use AdGuard Ad Blocker to set up DNS servers, including encrypted ones

快捷链接：下载 AdGuard 广告拦截程序

What is DNS cache?​

DNS cache stores the IP addresses of visited sites on the local computer so that they load faster next time. Instead of doing a long DNS lookup, the system answers the queries with DNS records from the temporary DNS cache.

The DNS cache contains so-called resource records (RRs), which are:

  • 资源数据（或 rdata）；
  • 记录类型；
  • 记录名字；
  • TTL（生存时间）；
  • 类别；
  • 资源数据长度。

当您可能需要清除缓存时​

You've changed your DNS provider to AdGuard DNS. If the user has changed their DNS, it may take some time to see the result because of the cache.

You regularly get a 404 error. For example, the website has been transferred to another server, and its IP address has changed. To make the browser open the website from the new IP address, you need to remove the cached IP from the DNS cache.

You want to improve your privacy.

如何在不同的操作系统上刷新 DNS 缓存​

iOS​

There are different ways to clear the DNS cache on your iPad or iPhone.

The simplest way is to activate the Airplane mode (for example, in the Control Center or in the Settings app) and to deactivate it again. The DNS cache will be flushed.

Another option is to reset the network settings of your device in the Settings app. Open General, scroll down, find Reset and tap Reset Network Settings.

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By doing that, you will lose connections to Wi-Fi routers and other specific network settings, including DNS servers customizations. You will need to reset them manually.

Android​

The easiest way to clear your DNS cache on your Android device is to turn the Airplane mode on and off. You can enable/disable the Airplane Mode in the Quick Settings pane.

A hard reboot can also help flush the DNS cache for your device. In order to do that, press and hold the power button for at least 20 seconds. It will (usually) force your device to reboot manually and the DNS cache will be cleared.

Another option is to reset the network settings of your device in the Settings app. Open Settings → System → Advanced → Reset options → Reset network settings and tap Reset Settings to confirm.

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By doing that, you will lose connections to Wi-Fi routers and other specific network settings, including DNS servers customizations. You will need to reset them manually.

macOS​

To clear the DNS cache on macOS, open the Terminal (you can find it by using the Spotlight search — to do that, press Command+Space and type Terminal) and enter the following command:

sudo killall -HUP mDNSResponder

On macOS Big Sur 11.2.0 and macOS Monterey 12.0.0, you may also use this command:

sudo dscacheutil -flushcache

After that, enter your administrator password to complete the process.

Windows​

To flush DNS cache on your Windows device, do the following:

Open the Command Prompt as an administrator. You can find it in the Start Menu by typing command prompt or cmd. Then type ipconfig/flushdns and press Enter.

You will see the line Successfully flushed the DNS Resolver Cache. Done!

Linux​

Linux does not have OS-level DNS caching unless a caching service such as systemd-resolved, DNSMasq, BIND or Nscd is installed and running. The process of clearing the DNS cache depends on the Linux distribution and the caching service used.

For each distribution you need to start a terminal window. Press Ctrl+Alt+T on your keyboard and use the corresponding command to clear the DNS cache for the service your Linux system is running.

To find out which DNS resolver you're using, command sudo lsof -i :53 -S.

systemd-resolved​

To clear the systemd-resolved DNS cache, type:

sudo systemd-resolve --flush-caches

On success, the command doesn’t return any message.

DNSMasq​

To clear the DNSMasq cache, you need to restart it:

sudo service dnsmasq restart

NSCD​

To clear the NSCD cache, you also need to restart the service:

sudo service nscd restart

BIND​

To flush the BIND DNS cache, run the command:

rndc flush

Then you will need to reload BIND:

rndc reload

You will get the message that the server has been successfully reloaded.

How to flush DNS cache in Chrome​

This may be useful if you do not want restart a browser every time during work with the private AdGuard DNS or AdGuard Home. Settings 1-2 only need to be changed once.

  1. Disable secure DNS in Chrome settings

    chrome://settings/security

  2. Disable Async DNS resolver

    chrome://flags/#enable-async-dns

  3. Press both buttons here

    chrome://net-internals/#sockets

  4. Press Clear host cache

    chrome://net-internals/#dns