Iptables Load Balancing Help

[crist...@gmail.com]

Hi to all.
I´m need to configure iptables with 2 ISP service provider and do not
have idea how to begin.
Actually I have configured my RH9 2.4.20 with one ISP working with
iptables perfectly. My boost is requesting me to add another internet
provider to the box and configure iptables with the newone. Also I need
to have load balancing with full tolerance.

The firsts doubt that I´ve are?

Do I to modify my iptables script adding the new data interface to the
same Rules?.

How can I do to masquerade using one public IP or the other one
dependig of the link status (I mean, if one goes down.. how to use
MASQUERADE for the live link) ?

I´ve a lot of questions. I´ll apreciate if somebody can help me.

Regards..