So, you are mixing terminology. Using the LMS and Backup LMS ip only is the old way of doing things, but it is fairly easy to configure.
HA Fast failover is the new way and that is the link I sent you above. HA Fast Failover still employs the LMS-IP and Backup LMS-ip, but it has other configuration elements and the failover is faster...
Please read the link I showed you above.