I can send packets but I receive nothing, routing problem

From: riviereg (guillaume_at_nomail.org)
Date: 09/03/04 

Date: Fri, 03 Sep 2004 16:46:27 +0700

Dear all linux networking,

I try to set up a route to my ISP:

my 10.0.0.0 network is connected to the router on eth0
my ISP is on link eth2 on my router (GNU/Debian sarge, kernel 2.6.8, I
try with 2.6.7 same problem).
my external IP is 1.2.3.4
my gateway is 1.2.3.5 (this is my modem, with a real IP address)

I try to route my internal IP 10.0.0.1 to this ISP

my route is configure like this:

# ADSL line
ip route flush table 5
ip route add table 5 default via 1.2.3.5 src 1.2.3.4 dev eth2
ip rule add fwmark 5 table 5

my Nat is like this

iptables -t mangle -A PREROUTING -s 10.0.0.1 -j MARK --set-mark 5
iptables -t nat -A POSTROUTING -o eth2 -s 10.0.0.1 -j SNAT --to 1.2.3.4

All is ok, I can access to my modem (1.2.3.5) from 10.0.0.1, I can also
access to internet on this modem (there is a web site on the modem).

But when I try to access to Internet from 10.0.0.1, I can "find" sites
but I receive nothing, all my ping are lost. This problem drive me crasy ...

I think I send packets but there is a kind of incoming reply routing
problem. All other IP's from my internal network can connect with the
default gateway on my first ISP (eth1).

Thank you for Help me on this,
Guillaume

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