How fast do DNS enteries apply?

For new DNS enteries, you can see the effect immediately (and sometimes not).

test.kossboss.com which was a cname change to www.google.com (so everytime i went to test.kossboss.com it would go to google – just for kicks). That change was instant.

Setting up graph.kossboss.com, which im sure is a new subdomain, took 2 to 3 hours. (i even timed it)

On changed DNS enteries (pointing new hostname to new IP) might take a moment, as old DNS cache has to clear out and flush out. Thats where the TTL field comes in. Hopefully its not too long on everything (yet long enough to ensure security, imagine if it was instant, and someone gained access to your DNS and changed it to point to their servers, the seemless repointing to the new servers would be determental to businesses – some services like certain Apache websites that use virtual hosts or SSL certs depend on good DNS enteries, so having that extra hour or day to fix or awknowledge the issue can save someones business – either way if that happens you can always circumvent that with your own static hosts file enteries)

Good info from other sites…

How long does it take for DNS Propagation?

Any time that DNS changes are made (on any level), you need to wait for propagation to complete. Propagation usually takes around 24 hours but is never usually more than 48. During propagation, traffic may come to either location. One person may see the new server while someone else sees the old one. Also, yourdomain.name may work while www.yourdomain.name does not. All of this is normal during propagation.

To speed things up on the internet, the Internet Server Provider (ISP) caches their DNS records. They create their own copy of the master record, and access it locally to search for website, each time someone tries to view it. This procedure speeds up internet activity, reduces the traffic and thus help the ISP work faster.

Each ISP caches the DNS record and updates it every few days. Each ISP has their own standard time frame to update the cache DNS record. This delay from your ISP will prevent you from viewing your website. This process is know as DNS propagation delay. The slow updating of the server cache is called propagation. The DNS information for your domain gets propagated across all server’s on the web. After this propagation  completes your website will be accessible to everyone on the internet.

In short, DNS propagation depends upon how frequently the DNS master cache nameservers of your ISP are refreshed.

So how fast do changes occur? (good answer on http://www.webhostingtalk.com/showthread.php?t=728168)

The timing of DNS changes vary from registrar to registrar. Some registrars, like NameCheap, are almost immediate.
The second part of the equation, is individual ISP’s. Alot of them cache A Records, so DNS changes are not felt immediately.
Last but not least, even your computer can cache an A Record. This can be resolved by closing any open browsers, and flushing the DNS. It won’t help if your ISP is still caching the old record though.
Sometimes things can be sped up if you ask your old host to update their DNS and point your domain to the new IP address. At the same time, you can login to your domain registrar and update the nameservers.
You can rent a dedicated IP from your Web Host, or even your own ISP (if your running your own server).

More good answers here? (info from here: http://support.launchrock.co/knowledgebase/articles/93950-what-is-dns-propagation-and-why-can-it-take-up-to)

What is DNS propagation?

To make viewing the web faster for their customers, ISPs cache all of their DNS records. This caching process is called Propagation.

Caching means that the ISPs read and display websites from their local files instead of looking them up on the Internet each time their customers want to view a website. This is similar, on a massive scale, to the way the browser on your computer caches websites to speed up browsing.

Propagation ultimately speeds up web surfing by 

  1. speeding up the return time it takes for a web browser to request a domain look-up and get an answer
  2. reducing the amount of traffic on the web therefore giving it the ability to work faster.

Why does propagation take so long?

The reason it takes so long for your LaunchRock (or any website) to be visible to everyone once you launch it, is that each ISP has an automated process that updates and caches DNS records every few days. Until their cache is reset, it will not display your launched website. There is not any kind of standard for this process, and they can set propagation time anywhere from a few hours up to 72.

Can you speed the process up?

Unfortunately, no. There is nothing that you, LaunchRock or anyone else can do to reduce DNS propagation time. It is simply a case of waiting for this automated process to complete.

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