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What is DNS Propagation?

 

If you have a new domain name, you must change the name servers to point to HostGator. This article will provide you some background information on DNS and what to expect when changing your name servers.


What is Propagation, and How Long Does it Take?

Propagation is the projected length of time it takes a domain's DNS (Domain Name System) information to be updated across the entire web after a change is made. The process can take 24-48 hours to complete in full. Because of propagation, not all visitors will be directed to your new name servers on your new hosting account; some visitors will continue to be directed to your old name servers on your old hosting account until propagation is complete.

How quickly visitors are directed to the new name servers depends on their physical location, internet service provider, and some luck; it is not something HostGator has control over. Once propagation is complete, your site will appear on our server, and your email will be fully functional.

There is no definitive way to tell when propagation is complete. During the first 48 hours, even if you can see your site on the new server, your next-door neighbor might still be seeing the site on the old server. This depends on three factors: your ISP, geographical location, and TTL. There are also ways for you to see the propagation progress using the websites below. These will show your website’s possible visibility. There are also ways for you to see the propagation progress using the websites below.

There are also ways for you to see the propagation progress using the websites below. These will show your website’s possible visibility.


How DNS Keeps You Connected

The routing of all communication between computers on the internet is handled by IP addresses rather than domain names. The following example should help you to visualize the process.

Like our telephone system, every active phone line has a phone number used to facilitate the connection of one line to another. To make a call, the phone that initiates the connection must have the number of the line to which it wants to connect.

In much the same way, your computer must find the correct IP address (of the website you want to visit) on the server before it can send the request to that server for a webpage. The same process applies to all other services (such as email, chat, or games) on the internet. DNS records function similar to a phone book, relating domain names with IP addresses to reach these services. To know your IP address, see this article: What is my connecting IP Address?


Functions of DNS Servers

DNS servers can handle one or both of two primary functions: DNS host and resolver. DNS hosts hold the zones for their domains and answer requests with the records from the zones for those domains. When you make changes to your zone, you are making changes to the host.

A resolver is a DNS server that will send requests to other DNS servers for the records from their zones to answer the requests that it receives. These sorts of requests are called recursive requests.

When you connect to the internet through your Internet Service Provider (ISP), your ISP will provide you with two or more resolvers responsible for handling the recursive DNS requests sent by your computer as you use the internet. In this reading, additional helpful points are being discussed: Pointing My Domain to HostGator When Using DNS Elsewhere.


Time To Live & Remote Caching

Since most DNS records don't change very often, most resolvers are configured to cache or store the results of previous lookups and respond to subsequent requests from the cached results for a period of time until the resolver decides that the cached copy is too old to be trusted. Propagation is the period it takes for the record cached on all resolvers everywhere to expire. In each record in the zone, there is a Time To Live (TTL) value that specifies (in seconds) how long a resolver should cache the record.

One technique to reduce the time it takes for changes to propagate is to reduce the TTL value in the current zone before making changes; however, the change in the TTL on the record itself will take the length of time specified in the original TTL value to propagate before propagation period is lowered for further changes. Also, some ISPs configure their resolvers to ignore the TTL value specified in the record altogether and cache the record for a length of time that they specify instead. Some resolvers are configured to cache records for up to 72 hours, although most are configured for less. Ultimately, time resolves propagation issues.

Note: While the TTL can be modified for a domain within the Zone File Records in cPanel, this will not affect the total time to propagate. This means that all custom TTL records set will unfortunately not be honored, as HostGator does not allow custom TTL.

DNS & Browser Caching

DNS Caching

Additionally, most computers cache DNS, which can cause the computer to "remember" the old IP address for up to 48 hours until the next time it updates. If your computer is caching the DNS, it may be possible to flush the DNS on your computer so that it looks up the IP address for the domain again.

Browser Caching

Browser caching has absolutely nothing to do with DNS; however, this can still cause you to see your old page content even after changing your DNS. Browsers will cache a copy of the page content previously viewed by the browser. You can clear your cache to get a fresh copy from the server.

For details on how to clear your cache, please read our articles on: