For most apps and servers, migrating the IP state is not enough. The app server's connection state cannot be easily migrated. E.g. The MySQL connection of a

For most apps and servers, migrating the IP state is not enough. The app server's connection state cannot be easily migrated. E.g. The MySQL connection of a failed MySQL server will be gone. Migrating the IP connection to a new MySQL server won't do anything. Carp is good for firewall server redundancy because IP state is all that firewall is maintaining.