I think most people who have a critical web server are likely to have a backup machine ready to go with the same configs as the primary. Using that method, all you would have to do is change the IP number of the secondary system to the primary IP and voila! This process would likely require some human intervention, though. You can be alerted of these failures, though with the monitoring scripts that I mentioned before. You don't have to have the scripts change anything themselves, just alert you of the problem. There are several monitoring packages out there that do exactly that. You don't have to program at all. The best one I've seen so far is Big Brother, and it's released under a fairly relaxed license. Hope this helps some. Other than switching IP's, I couldn't really come up with an automatic way of the redundancy you're looking for.