[LARTC] Multiple Gateway

["hail narcissus" <gene_yee@hotmail.com>]

I know this must have been asked MANY times, but there doesn't seem to be a 
search for the Archives.  I have read the HOW-TO docs and to be honest, it 
is extremely confusing.  I will re-read and hope to figure it out, but 
hopefully someone can help me out.

I have two connections coming into my server, on a DSL and the other a 
Cable.  Both connections go into two seperate firewalls.  One firewall is a 
Checkpoint firewall thich does static NAT to my server, the real IP is 
converted to 192.168.1.2.  The other firewall is just a WinRoute server with 
port forwarding, only have one IP, this is forwarded to 10.10.10.156.

The server is configured as:
eth0 -> 192.168.1.2 and GW 192.168.1.1  Primary SDSL Interface
eth1 -> 10.10.10.156 and GW 10.10.10.157  Secondary Cable Interface

The problem is that I want clients to connect to either connection to access 
my FTP server.  However packets are not necesarily exiting the same 
interface that they are coming in on, they always exit the GW highest in the 
routing list.  I am not sure if it is because of the NAT and port 
forwarding, but packets don't make it back to the destination unless it is 
going out the original interface.  I have verfied this by creating static 
routes and looking at the route cache.

I am only concerned about FTP traffic for eth1, which will have PASV and 
normal FTP traffic.  No other traffic will be port forwarded to this 
interface.

Possible solution, I don't understand IPROUTE2 yet so all of this is 
conceptual:

I can use IPTables to mangle all packets coming into eth1 and have them 
routed to go back out that interface.  From the HOWTo I am guessing:

1) Remove the default gateway pointing to 10.10.10.157.  This will leave all 
traffic going out 192.168.1.1
2) Mangle the packets, never done this, cut and paste out of HOWTO:
# iptables -A PREROUTING -i eth1 -t mangle -j MARK --set-mark 1
3) Then add a route for all marked packets to go out 10.10.10.157
Syntax is still very confusing to me, if this is the right approach I will 
try to figure out.  Hints are appreciated...

Does this make sense or am I looking into this at completely the wrong 
angle?

Thanks!!

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