If you are a hosting environment that is in more than one geographic location you will need to know DNS fail-over. This is a built in feature within DNS. Let’s say you are going to host a website, well you would configure your registrars DNS so that your A-Record’s (i.e. “www”, “@(no address)”) point to your hosting IP address, then from the host IP address you would be redirected to the appropriate header you specified for your domain (i.e. www.yourdomain.com). Now let’s say your company has gone global and you wanted redundancy for your site so that if one node failed your site wouldn’t be down because it would auto redirect to another IP Address. To do this all you would need to do it configure the same record with the different IP Address.
– Harry Caskey