If you are developing websites, then the chances are at some time or other you have been driven crazy when you have updated the DNS for a client’s website only to find that your web browser is returning an error, or serving the default Apache webpage.
So, you go and check the DNS out using something like MyIPTest.com only to find that everything appears to be correct.
The confusion can be further compounded by the fact that some tools rely on the operating system’s cache (as do web browsers), while others fetch fresh results. For example, you can ping domain.com on OSX, and get a completely different IP address to that returned by dig domain.com a
This is because sometimes, the operating system’s cache doesn’t update quickly enough, because the TTL values stored within it haven’t yet timed out – so it sees no reason to go and fetch new results – not while the cached IP is reachable.
So, that’s the why – here’s the how! Read More…