NAT with 2 Internet interfaces

Hello Everybody,
I have a Linux on PC as gateway (lets call it GW). GW has 3 interfaces. 2 of
them (ETH0, ETH1) have 2 different public IP adresses (IP_0, IP_1) and are
conneted via my ISP to the Internet. Third interface (ETH2) is a local
interface with not public IP (IP_2). In the local network there is a
computer (SERVER) with local IP(IP_S). Lets call this configuration Company.
I would like to connect to Company SERVER from home computer (IP_H), so I
redirected all traffic from my home computer to the SERVER:
/sbin/iptables -A INPUT -s IPH -d IP_0 -i eth0 -j ACCEPT
/sbin/iptables -t nat -A PREROUTING -t nat -s IPH -d IP_0 -j DNAT --to IP_S
/sbin/iptables -A INPUT -s IPH -d IP_1 -i eth1 -j ACCEPT
/sbin/iptables -t nat -A PREROUTING -t nat -s IPH -d IP_1 -j DNAT --to IP_S

I also have two routing tables with two default gateways on GW. If I ping
IP_0 from the Internet (not home computer) i have response from IP_0 and if
I ping IP_1 I have response from IP_1.

I understand that if I want my connection from HOME to SERVER works I have
to configure NAT for SERVER.

How do I have to configure this NAT???
I tried:
/sbin/iptables -t nat -A POSTROUTING -s IP_S -d 0.0.0.0/0 -o eth0 -j
MASQUERADE
/sbin/iptables -t nat -A POSTROUTING -s IP_S -d 0.0.0.0/0 -o eth1 -j
MASQUERADE

but it wont work.

If I leave MASQUARADE only on eth0 interface, then I can connect from home
to SERVER but only via IP_0. If i try to connect via IP_1, my packets going
to SERVER via IP_1 but returning via IP_0.

Please help me. I would like to choose if I connect from my home computer to
SERVER via IP_0 or IP_1.

Regards
Tomek

On 2005-04-14, Tomek <(E-Mail Removed)> wrote:
> Hello Everybody,
> I have a Linux on PC as gateway (lets call it GW). GW has 3 interfaces. 2 of
> them (ETH0, ETH1) have 2 different public IP adresses (IP_0, IP_1) and are
> conneted via my ISP to the Internet. Third interface (ETH2) is a local
> interface with not public IP (IP_2). In the local network there is a
> computer (SERVER) with local IP(IP_S). Lets call this configuration Company.
> I would like to connect to Company SERVER from home computer (IP_H), so I
> redirected all traffic from my home computer to the SERVER:
> /sbin/iptables -A INPUT -s IPH -d IP_0 -i eth0 -j ACCEPT
This is not needed here.

> /sbin/iptables -t nat -A PREROUTING -t nat -s IPH -d IP_0 -j DNAT --to IP_S
One "-t nat" will suffice.

> /sbin/iptables -A INPUT -s IPH -d IP_1 -i eth1 -j ACCEPT
This is not needed here.

> /sbin/iptables -t nat -A PREROUTING -t nat -s IPH -d IP_1 -j DNAT --to IP_S
One "-t nat" will suffice.

> I also have two routing tables with two default gateways on GW. If I ping
> IP_0 from the Internet (not home computer) i have response from IP_0 and if
> I ping IP_1 I have response from IP_1.
>
> I understand that if I want my connection from HOME to SERVER works I have
> to configure NAT for SERVER.
You have done it already (DNAT).

> How do I have to configure this NAT???
> I tried:
> /sbin/iptables -t nat -A POSTROUTING -s IP_S -d 0.0.0.0/0 -o eth0 -j
> MASQUERADE
> /sbin/iptables -t nat -A POSTROUTING -s IP_S -d 0.0.0.0/0 -o eth1 -j
> MASQUERADE
This is not needed here.
It would be necessary only for connections from SERVER to HOME. Then
you should use SNAT not MASQUERADE.

Jarek P.