Clustering a Firewall with 4 NICs (again)

[Osvaldo Mundim Junior <osvaldo@xxxxxxxxxxxx>]

Friends,

Help me in a question: I would like to do a load balancing with my firewall 
which has 4 network adapters. My question is: is it possible to do? does 
anybody has some experience with it? If it is possible, how would be the 
configuration?

some information:

                                 Internet
                                     |
                                  router
                                     |
                                     | eth3 = internet ip
 eth1 = internet ip  |---------|  eth2 = internet ip
     dmz1 -------|    firewall /  | ----- dm2
                            |     proxy     |
                            ----------
                                     |  eth0 = LAN ip (private)
                                   LAN

At this linux box Debian "potato" - kernel 2.4.18 -  (firewall) I have 
iptables, squid service and some static routes to my networks.

I want to create another linux box which will works with this existent 
firewall. On my dmz1, I have a Mail Server and on my dmz2 I have two DNSs and 
a Web Server.

some question:

How would I do to put those two firewalls (which is the dmz's and lan's 
gateway) to work together?


thanks in advance!
Osvaldo