iptables SNAT failing to work on second gateway.

Louis admin at isawgodtoday.info
Sun Jan 11 04:34:05 UTC 2009


i have two gateways.
gateway 1 == eth1
gateway 2 == ppp0
lan == eth0

eth1 is the deafault gateway(i do not want to change the deafault gateway)

SNAT works fine if i use eth1 and it's ip.

It fails when i try to use ppp0 and it's ip.

here is a screenshot that shows what is not working


how ever i kinda get it working when i do this(trying to force it's hand)

iptables -A PREROUTING -t mangle -i eth0 -s -j MARK 
--set-mark 1
iptables -t nat -A POSTROUTING -s -o ppp0 -j SNAT 
--to-source 60.241.215.xxx
ip rule add fwmark 1 table TPG

IPTRAF output:
ICMP echo req (60 bytes) from to on eth0
ICMP echo req (60 bytes) from 60.241.215.xxx to on ppp0
ICMP echo rply (60 bytes) from to 60.241.215.xxx on ppp0

so it gets close in that case but it will not forward the reply to

other info that might be of use:
root at 1:~# uname -r
i've patched kernel with http://www.ssi.bg/~ja/patch-2.6.27-ja1.diff 
made no difference.
same result when useing MASQUERADE

i hope this is enough infromation


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