Filipe Brandenburger wrote:
> Hi Fabian:
>
> On Tue, Jan 27, 2009 at 08:16, Fabian Arrotin <fabian.arrotin@xxxxxxxxxx> wrote:
>> Question is : how can i "mangle" output packets to appear coming from
>> public ip and not from 192.168.X.X ?
>
> Found this that might help you (google for: linux default outgoing ip):
>
> """
>> On a machine with multiple interfaces, is it possible to set the default
>> outgoing IP address to something other than the address for the interface
>> on the outgoing route?
>
> Yes.
>
> ip route add 10.1.1.0/24 via 192.168.1.1 src 172.16.1.1
> ^^^
> The src parameter tells the routing code to use this address when sending
> packets. The address only needs to be on the system. IE:
>
> ip addr add 172.16.1.1/32 dev dummy0
>
> And send the packets out of eth0.
> """
> From: http://lkml.indiana.edu/hypermail/linux/kernel/0112.1/0359.html
>
> Just make sure you keep a separate route for your ISP's side of the
> private network (maybe the one created when your interface goes up
> will do), otherwise your routing protocol might fail.
>
> HTH,
> Filipe
Hi Filipe,
thanks for the link, i completely missed that point from the 'ip route'
command.
On the other hand, 10 minutes after i had sent my mail (and 3 coffee
later to be precise) i saw also a picture from wikipedia
(http://upload.wikimedia.org/wikipedia/fr/thumb/3/3e/Netfilter_schema.png/400px-Netfilter_schema.png)
explaining how packets went through the different ip tables and it was
directly clear : even packets leaving the local box (and being processed
in the OUTPUT filter) are still processed in the nat table (postrouting
filter) so a simple SNAT rule did the job perfectly too ;-) In fact it's
the first time that i have to modify packets leaving a linux gateway and
i thought that only packets being forwarded (and so traversing the
FORWARD filter) could also being modified in the nat table ...
I've also had a look in the sysconfig.txt file to see how your solution
could be applied but it's still not very clear how that can be done. But
using GATEWAYDEV=eth3 (eth3 having my public-ip/32 while eth3:1 having
my 192.168.X.X/24 ip) in the /etc/sysconfig/network and declaring a
GATEWAY=192.168.X.X (isp router ip) in the ifcfg-eth3:1 does also the
job. But a `route -n` is strange though : " 0.0.0.0 0.0.0.0
0.0.0.0 U 0 0 0 eth3" like for the old ppp
stuff
So multiple ways to solve the initial question ...
--
Fabian Arrotin
idea=`grep -i clue /dev/brain` ; test -z "$idea" && echo "sorry, init
6 in progress" || sh ./answer.sh
--
--
Fabian Arrotin
idea=`grep -i clue /dev/brain` ; test -z "$idea" && echo "sorry, init
6 in progress" || sh ./answer.sh
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