OK, this should be pretty simple then, let me know if this works:

#!/bin/sh
# TCP Proxy using IPTables

IPTABLES=/sbin/iptables

echo 1 > /proc/sys/net/ipv4/ip_forward

# Flush nat table
$IPTABLES -t nat -F
$IPTABLES -F

# tcpproxy
$IPTABLES -t nat -A PREROUTING --dst 10.0.2.2 -p tcp --dport 8443 -j DNAT 
--to-destination 10.152.3.56:8443
## Don't need this line anymore, replace with a MASQUERADE target
#$IPTABLES -t nat -A POSTROUTING --dst 10.152.3.56 -p tcp --dport 8443 - j SNAT 
--to-source 10.0.2.2
$IPTABLES -t nat -A OUTPUT --dst 10.0.2.2 -p tcp --dport 8443 -j DNAT 
--to-destination 10.152.3.56:8443

$IPTABLES -t nat -A PREROUTING --dst 192.168.0.3 -p tcp --dport 8443 -j DNAT 
--to-destination 10.152.3.56:8443
$IPTABLES -t nat -A OUTPUT --dst 192.168.0.3 -p tcp --dport 8443 -j DNAT 
--to-destination 10.152.3.56:8443
$IPTABLES -t nat -A POSTROUTING -o eth0 -j MASQUERADE
$IPTABLES -t nat -A POSTROUTING -o eth1 -j MASQUERADE


On Wed, Jul 21, 2010 at 05:32:56AM -0700, nseritti wrote:
> Dan,
> 
> Here is the routing table:
> 
> r...@system:~# netstat -nr
> Kernel IP routing table
> Destination     Gateway         Genmask         Flags   MSS Window
> irtt Iface
> 10.152.3.1      0.0.0.0         255.255.255.255 UH        0 0
> 0 eth0
> 10.152.3.0      10.0.2.1        255.255.255.0   UG        0 0
> 0 eth0
> 10.0.1.0        10.152.3.1      255.255.255.0   UG        0 0
> 0 eth0
> 10.0.2.0        0.0.0.0         255.255.255.0   U         0 0
> 0 eth0
> 192.168.0.0     0.0.0.0         255.255.255.0   U         0 0
> 0 eth1
> 169.254.0.0     0.0.0.0         255.255.0.0     U         0 0
> 0 eth0
> 0.0.0.0         192.168.0.1     0.0.0.0         UG        0 0
> 0 eth1
> 
> The site to site is handled by a Cisco ASA at  10.0.2.1 allowing the
> eth0 network 10.0.2.2 system to route to the 10.152.3.0/24
> 
> 
> 
> 
> On Jul 21, 7:48 am, Daniel Eggleston <[email protected]> wrote:
> > On Tue, 20 Jul 2010 20:43:52 -0700 (PDT)
> >
> >
> >
> > nseritti <[email protected]> wrote:
> > > Hi,
> >
> > > I seem to be having trouble setting up an iptables proxy
> >
> > > My network looks like this:
> >
> > > Target system:
> >
> > > 10.152.3.56:8443
> >
> > > Internal System:
> > > eth0: 10.0.2.2
> > > eth1: 192.168.0.3
> >
> > > eth0 is connected to 10.152.3.0/24 network via site to site VPN
> >
> > > What I'm trying to do is allow users on the 192.168.0.0/24 network to
> > > point to 192.168.0.3:8443 and forward those requests to 10.152.3.56
> > > via eth0.
> >
> > > My current ruleset allows me to access the target system via eth0,
> > > however applying a similar ruleset to eth1 does not work. Below is the
> > > script I'm currently running which works on if connecting from the
> > > local system to it's eth0 address.
> >
> > > #!/bin/sh
> > > # TCP Proxy using IPTables
> >
> > > IPTABLES=/sbin/iptables
> >
> > > echo 1 > /proc/sys/net/ipv4/ip_forward
> >
> > > # Flush nat table
> > > $IPTABLES -t nat -F
> > > $IPTABLES -F
> >
> > > # tcpproxy
> > > $IPTABLES -t nat -A PREROUTING --dst 10.0.2.2 -p tcp --dport 8443 -j
> > > DNAT --to-destination 10.152.3.56:8443
> > > $IPTABLES -t nat -A POSTROUTING --dst 10.152.3.56 -p tcp --dport 8443
> > > - j SNAT --to-source 10.0.2.2
> > > $IPTABLES -t nat -A OUTPUT --dst 10.0.2.2 -p tcp --dport 8443 -j DNAT
> > > --to-destination 10.152.3.56:8443
> >
> > > Any help would be appreciated.
> >
> > > Thanks,
> >
> > > Nick
> >
> > We're missing some info.  You're SNAT-ing to a physical ethernet
> > adapter, when you should be SNAT-ing to the vpn net dev you didn't
> > mention.
> >
> > Post the output of these commands:
> >
> > ifconfig
> > netstat -rn
> 
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