--- On *Wed, 5/19/10, Ed Knapp <catbertek@hotmail.com>* wrote:

>
> From: Ed Knapp <catbertek@hotmail.com>
>
> Subject: Re: load balanced configuration
> To: "Main PLUG discussion list" <plug-discuss@lists.plug.phoenix.az.us>
> Date: Wednesday, May 19, 2010, 6:09 PM
>
>
> One thing struck me here with your description...
>
> “and a change to the DNS and we are off and running”
>
> While your DNS records might be changed relatively quickly during an
> incident, the change
> Itself can take quite a while to trickle down to the end users/clients out
> in the cloud.
> Any client’s DNS resolution that has not expired in the cache nor manually
> refreshed will
> still fail to properly resolve/connect.  It doesn’t usually, but I tell
> clients to plan for 48 hours
> Estimated time for the change to completely propagate.
>
> Some DNS services like UltraDNS can have your TTL set as low as 5 minutes
so you can change addresses quickly.  There are still some providers that
ignore the time to live setting though and cache answers longer.