I have an exchange 2010 server with all roles. I have a backup exchange box off-site and wanted to get it setup so if the main one dies I can have the backup resume. Used to use 3rd party applications to do this but I hear its easy to do with exchange 2010? What all is required to setup and if a disaster occurs, how do you get the other one active (dns change internally and change mail delivery from firewall to hit backup server?).