[LARTC] Route all LAN traffic through eth2 and keep web/mail traffic on eth0

[Eduardo Bejar]

Hi, 

I have the following config:

1 PC with 3 NICs, that shares internet connection to LAN. 
eth0 uses a public IP ($public_ip_1)
eth1 uses a private IP ($private_ip)
eth2 uses a public IP ($public_ip_2)

I have a webserver and a mailserver accesible by $public_ip_1 (eth0)
I have a LAN with all terminals using private IPs, and $private_ip (eth1) as
gateway.
$public_ip_1 and $public_ip_2 are from the same network segment (two
consecutive IPs).
eth0 and eth2 should use the same external IP as gateway (only 1 provider,
so this is not a load balancing/multiple providers case).
eth0 and eth2 are connected to the same switch.

How can I route all LAN traffic via eth2 and keep web/mail traffic on eth0?
And with this, make the LAN traffic use eth2's IP to connect to the Internet
and the PC traffic use eth0?

I tested masquerading through eth2 with
iptables -t nat -A POSTROUTING -s $private_ip_net/255.255.255.0 -o eth2 -j
MASQUERADE

But LAN could not access the Internet, although the PC could.

Someone told me something about ip rules, which I tested but it seems that
they did not worked as both eth0 and eth2 should use the same gateway.

Please send me any comments/help regarding this issue, 

Thanks!

Edo