Talking about the caching problem of domain name DNS

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Can see from many places, many just started to do the station friend, the domain name establishment aspect knowledge principle is not enough, so that for some test needs, often to the domain name resolution. Today, change a record, tomorrow again ns. Or, when migrating a domain name, migrating the site due to some wrong operation, leading to avoidable problems, under improper operation there are problems.

Domain name resolution is not the same as space-bound IP, can be immediately effective, immediate failure.

Each domain name, in the service provider there is a DNS server, the role is to facilitate the user memory of the domain name to facilitate the computer to understand the IP address, in the domain name management, one of the records of your domain name point, the term is called a record, used to point to an IP address.

But people all over the world visit your site through the Internet, through domain name addressing, access to your domain Name Service provider's DNS server, get your designated IP address. Then successfully log on to your website.

But not every time you visit your site, you will go to your service provider DNS server to query the IP address. Usually your city ISP (Network service provider) will have a DNS server that caches your domain name on your first visit. The next time you visit, he will transfer the IP you have pointed to from the cache.

At this point, the problem comes. If you re pointing to a new IP in the service provider background. And each city's DNS servers do not know, then users visit your site, but also access to the old IP, resulting in the site can not open. Typically, local DNS servers will be addressable over a period of time to locate your new IP address.

Unfortunately, the local DNS refresh time is unknown, some fast, some slow. Of course, if the service provider's DNS server is not good, can not provide timely synchronization, will also cause the domain name can not be resolved to the new IP address. This is why some service providers domain name registration is particularly cheap, and some of the reasons for the more expensive.

In the case of common domain name parsing operations, in your domain DNS server is more normal, add a new resolution record, the effective time is within 1 hours. Modify the resolution record, the effective time is 6 hours, generally speaking, not more than 12 hours.

In recent times, because of GoDaddy domain DNS in the domestic individual areas, frequency by the relevant operators shielding, resulting in these areas can not visit the site. Some use GoDaddy domain name DNS webmaster, including the site (from yesterday's domain name can not be resolved to talk about GoDaddy domain name DNS.) ), forced to turn DNS back to the country. Most personal webmaster will transfer domain DNS to a domestic provider of free DNS service provider "Dnspod" there.

Here is a modification of the domain name NS records (that is, DNS server domain name), compared to domain name resolution, to modify the domain name NS, the effective process is very long, to all parts of the world into force, may be slow to less than 72 hours.

In the modification domain DNS, the domain name of the old Control Panel on the resolution records do not immediately delete, to ensure that the new and old DNS alternate time to ensure that the domain name resolution of the balance transition, will not interrupt the resolution. However, for the old domain DNS must be deleted all, so as to avoid the phenomenon of parsing confusion.

and the domain name TTL, that is, the domain name record effective period, the proposal more than 600, not too long, also not easy too short, too long will lead to the domain name resolution effective time, too short will aggravate the DNS burden, resulting in analytic instability.

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