Please allow up to 48 hours for DNS changes to be effective.

Why will it take up to 48 hours?

To your computer, everything is a number. After all, computers are much better at processing numbers than anything else. Unfortunately, we aren't quite as good at numbers and we prefer words. When it comes to website addresses, DNS helps bridge that gap.

Every computer on the internet has a unique number, called an IP address. When you visit a website, you are connecting to the IP address of the website’s server and you are receiving information from that website's server through that connection. In order to request a web page, you need to know the IP address of the website’s server. More specifically, your computer needs to know the IP address so that it will know what website you want to connect with. DNS to the rescue!

DNS stands for Domain Name Server and is a collection of servers that act like a phone book, storing an extraordinarily long list of domain names and their corresponding IP addresses, When you type "www.notjustcomputers.co.uk" into your web browser, it connects first to your Internet Service Provider's DNS server and asks it for the IP address that corresponds to the domain name "www.notjustcomputers.co.uk". If everything goes well, the DNS server replies with something like 87.194.70.68, and your web browser will then communicate with the www.notjustcomputers.co.uk web servers and you will be able to exchange information.

If you were to call your long lost friend, you would take out your phone book and look up their name (www.notjustcomputers.co.uk) to find the associated number (87.194.70.68). When you call the number, you are connected through to their house (server), where you finally talk to your friend (exchange information).

A phone book is updated yearly, while a DNS server is updated every 24-48 hours and this is why there is a wait period of 48 hours before your domain name will start pointing to the website that you are pointing it to.

My site is showing! already...

You may see either the old or new location until the 48hrs is up, just because you can see the new location does not mean everyone will see the same therefore you should not really shout about it until after 48hrs as your visitors DNS Servers may have cached results which could take them to the old site.

What is Caching?

Caching is where a computer remembers, with DNS Records they have a TTL (Time to Live) this is normally 86400 seconds (24hrs), the reason for this is to reduce the number of queries on your DNS servers, lowering this value can have adverse affects on the performance of your site and if there is a problem with your DNS servers may result in people not being able to resolve and connect to your site.

Planning a DNS Change

If you are planning to make a change to DNS then you can lower the TTL to 3600 seconds (1 hour), this should be done at least 48hrs before the planned change, this tells the DNS server to recheck every 1 hour for changes (if only life were that simple!), some ISP's ignore this setting and only refresh their Cache every 24 hours, so whilst it does not update for everyone in an hour it will most likely update for a lot of people.

In Summary

When making DNS changes you MUST wait 48 hours before sending an marketing material, and even then check from several locations first!