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What is the principle and function of DNS? For this problem, this article introduces the corresponding analysis and solution in detail, hoping to help more small partners who want to solve this problem find a simpler and easier way.

Azure's failure this time is very quiet in China and very lively abroad, indicating that there are still few people using Azure in China.

The Microsoft cloud outage lasted about three hours. The official explanation is that because of human factors, DNS configuration is wrong.

What is DNS? It was actually so powerful that it caused a cloud giant to malfunction for three hours. Today we are going to talk about DNS.

DNS is an abbreviation for Domain Name System, which is a core service of the Internet. It serves as a distributed database that can map domain names and IP addresses to each other, making it easier for people to access the Internet without having to remember IP addresses that can be read directly by machines. This is the official DNS statement. To put it bluntly, the main role of DNS is to "translate" familiar URLs (domain names) into IP addresses that computers can understand. This process is called DNS domain name resolution.

To summarize, DNS services resolve domain names to IP addresses. DNS can also resolve a domain name to multiple IPs, so it can also be used for Load Balancer.

Let me explain how DNS works, using www.xttblog.com as an example. When we visit the website, the browser will first query the cache to see DNS information, that is, to see if there is IP information for the website in the cache, and if there is, then visit it directly.

If it's not in the browser cache, it's going to get it from the operating system, you know "www.xttblog.com"? The operating system also caches IP information. If there is one in the operating system cache, the corresponding IP is directly accessed. If there is no IP, the domain name resolution is performed according to the preferred DNS server configured on the operating system.

Similarly, if there is a corresponding resolution address on the preferred DNS server, it returns to directly access the corresponding IP. If not, a query is initiated to the upper DNS server. In this way, layer by layer to resolve, until the root domain name server. There are 13 root DNS servers in the world, but none of them are in China. If the root domain name is not resolved, it is likely that your domain name is wrong.

This is how DNS works. According to this principle, in fact, sometimes, we QQ, WeChat and so on can be used normally, but can not open the web page, it is likely to be DNS problems.

Hackers will also use this principle to hijack websites using DNS, secretly insert advertisements/induce/sniff account passwords, etc.; even some computer room personnel abuse their power for personal gain, which will affect users 'Internet speed and Internet experience, account security, etc. In short, there are many DNS related issues that occur around the world every year.

The following is a list of some common DNS information used in China.

114 DNS： （114.114.114.114;114.114.115.115）

DNS Security (114.114.114.119;114.114.115.119)

DNS Home Edition (114.114.114.110;114.114.115.110)

AliDNS: (223.5.5.5; 223.6.6.6)

Baidu BaiduDNS (ipv4 address: 180.76.76.76;ipv6 address: 2400:da00:: 6666)

DNSPod DNS+(Tencent public DNS, first two recommended)(119.29.29.29; 119.28.28;182.254.118.118;182.254.116.116)

China's first IPv6 public DNS: preferred DNS: 240c::6666, backup DNS: 240c::6644.

About the principle and role of DNS is what the answer to the question is shared here, I hope the above content can be of some help to everyone, if you still have a lot of doubts not solved, you can pay attention to the industry information channel to learn more related knowledge.

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