I have a proxy server with two nics, each pointing to a different router and a different internet connection.

example:

eth0 -> 192.168.1.2 -> 192.168.1.1
eth1 -> 10.0.0.2 -> 10.0.0.1

The gateway of the machine itself is 192.168.1.1 and thats how I want it.

but squid is using this for its default path to the internet, and I want it to use 10.0.0.1.

Is this possible without changing the machines gateway?

You haven't described which is your LAN interface and which is your WAN interface?

You have not required to add default gateway on you LAN interface. Just require to configure it on WAN Interface.

Both interfaces (eth0 and eth1) are both LAN and WAN interface. meaning they both have seperate LANs and both are connected to different WANs (internet connections).

I dont understand how this configuration going to help you? It is good to have squid as your internet gateway.

Well here is the problem...

I have a linux box, it serves as an SFTP server for huge files (TIF and PSD files) for external clients. It also servers as proxy server for internal hosts.

There are two routers connected to 2 different ISP's.

ISP1 -> router1 -> eth0

ISP2 -> router2 -> eth1

So right now the ISP on eth1 is not being used. all traffic in and out is going over eth0 because squid is using the default gateway.

Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
10.0.0.0 * 255.255.255.0 U 0 0 0 eth1
192.168.1.0 * 255.255.255.0 U 0 0 0 eth0
169.254.0.0 * 255.255.0.0 U 0 0 0 eth1
default 192.168.1.1 0.0.0.0 UG 0 0 0 eth0


The problem is when people are downloading 50 PSD files at 200MB each the internet really slows down for the folks using the proxy server. And all this time the second ISP is getting NO bandwidth usage.

So if I change the default gateway to eth1, then the people using SFTP can not connect because they come in on eth0, but the box tries to respond on eth1 the new default gateway.

So I need SFTP to work on eth0 and squid to work on eth1.

Did I explain that clear? ANY help would be appreciated.

This link might help you to resolve your problem.
http://lartc.org/howto/lartc.rpdb.multiple-links.html

For anyone reading this in the future this is how I resolved the issue:

1) Add new table to /etc/iproute2/rt_tables
echo -e "200\tAivilaNet" >> /etc/iproute2/rt_tables

2)Add new route to interface
echo "default table AivilaNet via 10.0.0.1" > /etc/sysconfig/network-scripts/route-eth1

3) Add new rule to interface
echo "from 10.0.0.2 table AivilaNet" > /etc/sysconfig/network-scripts/rule-eth1

mark this as resolve.