[LARTC] NAT over 2 providers (not load balance)

[Tóth Nándor]

Hi!

Mihai Vlad wrote:
> Hi guys,
> 
> Can you take a look at this? :)
> 
> 
> 		+-----------+
> 		|           |
> 	 eth1-|-          |
> 		|          -|-eth0---LAN---
> 		|           |
> 	 eth2-|-          |
> 		|           |
> 		+-----------+
> -
> 
> eth0 is connected to the LAN having the IP=LAN_IP
> 
> eth1 is connected to the first  ISP having IP=ISP_IP_1 and GW=ISP_GW_1
> eth2 is connected to the second ISP having IP=ISP_IP_2 and GW=ISP_GW_2
> 
> I need to selectively SNAT clients in the LAN to ISP_IP_1 or ISP_IP_2.
> 
> That would be something like:
> $IPTABLES -t nat -A POSTROUTING -s 172.17.31.5 -j SNAT --to-source $ISP_IP_1
> $IPTABLES -t nat -A POSTROUTING -s 172.17.31.7 -j SNAT --to-source $ISP_IP_2
> 
> 
> This does not work since all the packets are forwarded to the default GW
> which is ISP_GW_1.
> 
> How can I change this?
> 
> As far as I remember, the routing decisions and policy are before the
> POSTROUTING chain in which the SNAT occurs...

$IPTABLES -t nat -A POSTROUTING -o $EXTERNAL_INTERFACE  -j SNAT 
--to-source $EXTERNAL_IP_ADDR
$IPTABLES -t nat -A POSTROUTING -o $EXTERNAL_INTERFACE2  -j SNAT 
--to-source $EXTERNAL_IP_ADDR2

And add some rules based on client's source ip address. (policy routing)
http://www.linux.com/howtos/Adv-Routing-HOWTO/lartc.rpdb.simple.shtml


-- 
Udv,
   Nandor