Anyone know how to use primary and secondary ip in iax.conf?

Hi,

Can anyone point me out to the documentation or had any experiences for using server and altserver ip for failover in iaxprov.conf?

I just need to failover between to asterisk servers. And how to go about it. Do both servers need to have the same database or point to the same sql database?

I use asterisk@home which is database driven for configuration and extensions. Any suggestion?