DNS中断可能会让任何受其影响的人感到头疼。遇到问题的网站可能会导致糟糕的用户体验，并可能导致企业蒙受金钱损失。
DNS 表示域名系统(Domain Name System)。它是一个将 IP 地址与域名相匹配的Internet目录。(Internet)每个(Every)网站都有自己的网络 IP 地址。用户可以键入网站的 IP 地址来访问网站。但是，它们很难记住。因此，大多数人改用域名。
DNS服务器将用户指向正确的位置，以便网站正确加载。当您无法连接到 IP 地址时，会发生DNS错误。(DNS)这种类型的中断通常是因为您失去了Internet或网络连接。
偶尔的 DNS(Occasional DNS)中断是不可避免的。但是，并非所有这些都是重大攻击，并且可以相对容易地解决。
首先检查基础知识(Check the Basics First)
并非所有连接问题都是 DNS 问题(are DNS issues)。例如，如果没有插入路由器，您将无法连接到Internet。但这不是DNS问题。
通过检查以下内容，可以轻松修复一些DNS中断：(DNS)
- 检查您的域名服务器。如果您更换了托管公司或域名注册商，它们可能不正确且易于修复。
- 如果您最近对名称服务器进行了任何更改，它们需要时间在网络上传播。这可能需要 24 到 48 小时。
- 通过关闭路由器重新启动(Reboot)路由器，等待一分钟，然后重新打开。
- 检查以确保所有连接和电缆均已正确插入。
- 运行恶意软件扫描以查看是否有病毒阻止您的Internet访问。
- 如果您无法访问特定站点，则可能是该网站的问题，而不是您的连接问题。一种检查方法是选择Down for Everyone 或 Just Me(Down for Everyone or Just Me)。
是你的路由器吗？(Is it Your Router?)
路由器有自己的CPU、内存、主板，甚至操作系统。所有这些组件都管理数据流量。这些路由器组件可能会过载。这与在笔记本电脑上同时打开太多浏览器导致其死机的概念相同。
当您通过路由器向许多设备发送大量数据时，它可能会减慢或完全停止工作。此外，大多数家庭计算机Internet连接都使用动态 IP 地址。ISP(ISPs)在特定时间段内为每个调制解调器分配一个 IP 地址。
当此时间到期时，您的ISP将向您的调制解调器发送一个新的 IP 地址。但是，如果您的路由器非常繁忙，它可能无法收到带有新 IP 地址的消息并继续尝试使用旧的过期地址。
如果路由器的通风孔被灰尘或电缆堵塞，它可能会过热。因此，请确保它们没有被阻止。
要重新启动路由器，请按照以下步骤操作：
- 关闭路由器并拔下电源线。
- 拔下(Unplug)构成网络的任何其他接入点，例如调制解调器。
- 等待 20 到 30 秒。
- 重新插入所有内容。
- 重新打开路由器电源按钮。
- 等待 30 到 60 秒。
等待为您的路由器提供建立稳定连接所需的时间。如果您没有连接、无法连接到Internet或您的设备未显示您的网络可用，请尝试重新启动您的路由器。
更深入的故障排除(More In-Depth Troubleshooting)
如果上述步骤未能解决您的问题，则可能是以下常见DNS问题之一。
DNS缓存
计算机存储有关尝试和最近访问网站的网络信息。
此缓存有时会损坏。要刷新缓存，请在命令提示符中输入以下内容：
ipconfig /flushdns
这将清除缓存，以便您下次访问同一网站时，将更新DNS信息。(DNS)
您的域名
如果您的网站地址正常，但没有指向您的网站，则可能是您忘记更新您的域名。快速联系您的域名注册商，看看是否可以取回。
TCP/IP 设置
Transmission Control Protocol/Internet Protocol( TCP/IP ) 是定义计算机如何与其他设备通信(communicate with other devices)的设置。
对于IPv6和IPv4属性，设置应设置为自动获取 IP 地址(Obtain an IP address automatically)和自动获取 DNS 服务器地址(Obtain DNS servers address automatically)。
要了解如何检查这些设置，请阅读：
还没有解决？(Still Not Resolved?)
如果上述解决方案都不能解决您的DNS中断问题，则可能是导致问题的配置错误或错误。
Windows 有一个名为nslookup(nslookup)的内置工具。它可用于对DNS命令进行故障排除以确定特定的内部或外部问题。
可能导致问题的最常见的DNS记录是：
- CNAME（规范名称(Canonical Name)）将一个域名指向另一个域名。
- A记录是与 IP 地址匹配的域的基本DNS数据(DNS)。
- MX（邮件交换(Mail Exchange)）记录从您的域到主机服务器的直接电子邮件。
如需完整教程，请观看使用 Nslookup 解决 DNS 问题(Troubleshoot DNS with Nslookup)。
试用工具(Try Tools)
如果您仍然遇到DNS问题，请尝试以下工具之一来帮助诊断和解决您的问题。IntoDNS是一个免费工具，可以检查DNS记录的配置和健康状况。
它提供了一份报告，其中包含有关如何解决参考协议官方文档的问题的建议。
OpenDNS 的缓存检查是一种工具，可以对(OpenDNS’ Cache Check)OpenDNS如何解析您的域提供独特的见解。它使用所有OpenDNS(OpenDNS)服务器直接查询您的域并报告结果。
Network Tools提供免费的网络工具，包括NS Lookup、DNS Lookup以及域和主机信息。
采取预防措施并做好准备(Take Precautions & Be Prepared)
在某些时候，所有网站都会经历一些停机时间。没有任何服务可以保证 100% 的正常运行时间。
当高调的云中断发生时，我们都看到了头条新闻。但是，您可以采取一些预防措施来保护您的业务免受DNS中断的影响。
- (Use)在不同位置和不同服务器上使用多个DNS服务提供商。(DNS)
- (Separate)将外部DNS服务器与内部服务器分开。
- 使用(Use)不同的域供公共和内部使用。
- DNS服务提供商应与域名注册商分开。
- 避免需要基于 Web 的控制面板来更新配置的提供商。而是设置一个DNS服务器，该服务器将从不公开的DNS区域传输中更新您的信息。(DNS)
- 在您的注册商帐户上使用(Use)双重身份验证。
监控您的 DNS 服务器(Monitor Your DNS Server)
网络犯罪分子正在寻找传播恶意软件和感染计算机系统的新方法。
密切关注您的DNS服务器活动可以提醒您性能不佳或中断的迹象。积极主动地监控DNS的正常运行时间和性能。在问题发生时检测(Detect)问题，以确保您的网站访问者拥有积极的用户体验。
DNS Tools提供了一套监控工具，可以实时了解您的DNS配置在Internet上的执行情况。
如果您遇到问题，请尝试上述建议来解决您的DNS中断问题。
How to Avoid and Resolve DNS Outages
DNS outages can cause headaches for anyone affected by them. Sites experiencing issues can result in bad user experienсe and possible loss of money for the business.
DNS means Domain Name System. It is an Internet directory that matches IP addresses with domain names. Every website has its own web IP address. Users can type a website’s IP address to visit a site. However, they are difficult to remember. So, most people use the domain name instead.
DNS servers point users to the right location so that websites will load correctly. DNS errors happen when you are not able to connect to an IP address. This type of outage usually occurs because you have lost the Internet or network connection.
Occasional DNS outages are inevitable. However, not all of them are significant attacks and can be solved relatively easily.
Check the Basics First
Not all connectivity issues are DNS issues. For example, if a router is not plugged in, you won’t be able to connect to the Internet. But it is not a DNS problem.
Some DNS outages can be fixed easily by checking the following:
- Check your domain nameservers. If you have switched your hosting company or domain registrar, they may be incorrect and simple to fix.
- If you have recently made any changes to your nameservers, they need time to propagate across the web. This may take from 24 to 48 hours.
- Reboot your router by turning it off, wait a minute, and then turn it back on.
- Check to make sure all your connections and cables are correctly plugged in.
- Run a malware scan to see if a virus is blocking your Internet access.
- If you are having trouble reaching a specific site, it could be an issue with the website and not your connectivity. One way to check is to go to Down for Everyone or Just Me.
Is it Your Router?
Routers have their own CPU, memory, motherboard, and even an operating system. All of these components manage data traffic. These router components can get overloaded. This is the same concept as having too many browsers open at once on a laptop that causes it to freeze.
When you are sending lots of data through your router to many devices, it can slow down or stop working altogether. Also, most home computer Internet connections use dynamic IP addresses. ISPs assign an IP address to each modem for a specific time period.
When this time expires, your ISP will send your modem a new IP address. However, if your router is very busy, it might not get the message with the new IP address and keep trying to use the old expired one.
If the router’s ventilation holes are blocked by dust or cables, it can overheat. So, make sure they are not blocked.
To restart your router, follow the steps below:
- Turn off the router and unplug it.
- Unplug any other access points such as a modem that make up your network.
- Wait between 20 and 30 seconds.
- Plug everything back in.
- Turn the router power button back on.
- Wait for 30 to 60 seconds.
Waiting gives your router the time it needs to establish a stable connection. Try restarting your router if you have no connectivity, are unable to connect to the Internet, or your device doesn’t show your network as available.
More In-Depth Troubleshooting
If the steps above didn’t resolve your issue, it could be one of the following common DNS problems.
DNS Cache
Computers store networking information on attempts and recent visits to websites.
This cache can sometimes become corrupted. To flush your cache, enter the following into the command prompt:
ipconfig /flushdns
This will clear the cache so that the next time you visit the same website, the DNS information will be renewed.
Your Domain Name
If your website address is working but not directing to your site, it could be that you forgot to renew your domain name. Contact your domain registrar quickly and see if you can get it back.
TCP/IP Settings
Transmission Control Protocol/Internet Protocol (TCP/IP) are the settings that define how computers communicate with other devices.
For IPv6 and IPv4 properties, the settings should be set to Obtain an IP address automatically and Obtain DNS servers address automatically.
To learn how to check these settings, read:
Still Not Resolved?
If none of the above solutions resolve your DNS outage, it could be a misconfiguration or error that is causing the issue.
Windows has a built-in tool called nslookup. It can be used to troubleshoot DNS commands to determine the specific internal or external issues.
The most common DNS records that can cause issues are:
- The CNAME (Canonical Name) points one domain name to another.
- The A records are the basic DNS data that match domains with IP addresses.
- MX (Mail Exchange) records direct emails from your domain to a host server.
For a full tutorial, watch Troubleshoot DNS with Nslookup.
Try Tools
If you are still having DNS issues, try one of the following tools to help diagnose and fix your problem. IntoDNS is a free tool that will check the configuration and health of DNS records.
It provides a report with suggestions on how to fix issues referencing protocols official documentation.
OpenDNS’ Cache Check is a tool that gives unique insights into how OpenDNS resolves your domain. It directly queries your domain using all OpenDNS servers and reports the results.
Network Tools provides free network tools including NS Lookup, DNS Lookup, and domain and host information.
Take Precautions & Be Prepared
All websites will, at some point, experience some downtime. No service can promise 100% uptime.
We have all seen the headlines when high-profile cloud outages occur. However, there are some precautions you can take to keep your business safe from DNS outages.
- Use more than one DNS service provider in different locations and on different servers.
- Separate external DNS servers from internal servers.
- Use different domains for public and internal use.
- The DNS service provider should be separate from domain name registrar.
- Avoid providers that require web-based control panels to update configurations. Instead set up a DNS server that will update your information from a DNS zone transfer that is not available publicly.
- Use two-factor authentication on your registrar account.
Monitor Your DNS Server
Cybercriminals are finding new ways to spread malware and infect computer systems.
Keeping an eye on your DNS server activity can alert you to signs of poor performance or outages. Be proactive and monitor uptime and performance of your DNS. Detect problems while they are occurring to ensure your website visitors have a positive user experience.
DNS Tools offers a suite of monitoring tools to get real-time insights on how your DNS configurations are performing on the Internet.
If you encounter a problem, try the above suggestions to resolve your DNS outage.
