Changing NameServers and DNS Cache

Ever change a nameserver at your Domain Registrar and wonder why it takes so long for the domain to point to your new web site? The answer may be that you are using a DNS Caching service such opendns.com or google’s public dns. The Cache doesn’t update automatically but on a set schedule. If you don’t want to wait, your caching service may allow you to refresh it manually. For instance, both Google and Opendns allows anyone to flush the Cache for a particular domain without even logging in:

1. Refresh the OpenDns cache
2. Refresh Google Public DNS

Open DNS refresh page is particularly helpful as it shows locations of all of its DNS servers throughout the world and the ip address that each has listed for your domain. Even if you don’t use OpenDNS this give you a great visual of how a change in your nameserver propogates the change in your web servers’ ip throughout the internet. If after flushing the cache the servers reflect the correct IP address for your webserver, you know that any delays in DNS propogation are likely due to DNS caching and/or local DNS cache or configuration.

Another thing to keep in mind is that you may need to flush the DNS Cache on your own website. On Windows this is done by opening a Command windows and typing

ipconfig /flushdns

It should return with

Windows IP Configuration
Successfully flushed the DNS Resolver Cache.

One other tip: if you are curious to know whether others are experiencing resolution issues, go to an online proxy site such as Zend2.com, type in your domain, and see the result. Often you will see the new website here before you see it locally. Timings differ due to the time it takes to propagate through the internet and caches to be updated.

Some helpful reference links:


• How DNS Works
• How Domain Name Servers Work