Fabian Arrotin wrote: > Filipe Brandenburger wrote: >> Hi Fabian: >> >> On Tue, Jan 27, 2009 at 08:16, Fabian Arrotin <fabian.arrotin at arrfab.net> 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 ... > one coffee cup later i see in sysconfig.txt documentation file for the paramaters of ifcfg-<interface-name> : "SRCADDR= use the specified source address for outgoing packets" .. so definitely resolved by sysconfig files (so a clean solution) -- -- Fabian Arrotin idea=`grep -i clue /dev/brain` ; test -z "$idea" && echo "sorry, init 6 in progress" || sh ./answer.sh
