I have 3 web/mail servers running in 3 different locations with 3 different wan ips (go figure). Right now the primary is setup as www.mydomain.com, then theres www2 and www3. www2 and www3 are just offsite mirrored backups of www, I have no use for a www2 or www3. They just sit there in the even that our primary server goes down. What I'd like to do is setup some sort of dynamic dns system that repeatedly pings my primary server. If the server doesn't respond, then I'd like the DNS info to change from my primary server's wan ip, to www2's wan ip. Then as soon as the primary server comes back online the DNS info automatically gets reset to it's wan ip.

First of all I'd like to know if this was possible, and if so, how I could go about setting this sort "auto dns failover" up. Thanks!

what you want to do is possible, in fact its very common.
type "dig yahoo.com" you want to set up something like that, correct?
I've never done this before either, but you should be able to just add another host entry into your dns server with the same domain name, only a different address. If i'm wrong someone please correct me.

I also think it'd be cool to setup an auto failover cluster. That would probably also give me the same result. As soon as the primary server goes offline the secondary machine would begin to receive all requests automatically.

Edit: I understand the concept of all of this but I'd really like to be pointed in the direction of how to do it. Thanks again!