Re: How to masquerade when using ROUTE

[Glaucius Djalma Pereira Junior <glaucius@gmail.com>]

irc channel is better than an IM program

see you there

On 5/9/05, Taylor, Grant <gtaylor@riverviewtech.net> wrote:
> > I want to route all outgoing port-25-traffic produced by the clients
> > over ppp1. The rest schould take the default route over ppp0.
> >
> > I used the following command:
> >
> > iptables -A PREROUTING -p tcp --dport 25 -t mangle -i eth0 -j ROUTE
> > --oif ppp1
> 
> This seems reasonable enough.
> 
> > But the source addresses of the packets are wrong as "tcpdump -ni ppp1"
> > shows:
> >
> > 01:20:24.422756 IP 192.168.0.4.32825 > 160.45.10.13.25: S
> > 2020082843:2020082843(0) win 5840 <mss 1460,sackOK,timestamp 266850[|tcp]>
> >
> > 192.168.0.4 is the IP adress of the client which tried to connect to the
> > mailserver 160.45.10.13.25.
> >
> > Masquarding is done to 192.168.0.0/24:
> >
> > # iptables -t nat -L POSTROUTING
> > Chain POSTROUTING (policy ACCEPT)
> > target     prot opt source               destination
> > MASQUERADE  all  --  192.168.0.0/24       anywhere
> >
> > My default route is set to ppp0.
> >
> > So, how can I replace/masquerade the 192.168.0.4 by the official IP
> > address of ppp1?
> 
> It looks like there might be a chance that traffic that goes out ppp0 and ppp1 are matching your one POSTROUTING rule.  Is there a reason that you are not specifying an interface the traffic is going out to match against?  I.e.
> 
> iptables -t nat -A POSTROUTING -o ppp0 -j MASQUERADE
> iptables -t nat -A POSTROUTING -o ppp1 -j MASQUERADE
> 
> I'm wondering if there is not some confusion in the kernel / routing code as to which source IP to use when going out ppp1.
> 
> 
> Grant. . . .
> 
> 


-- 
Glaucius Djalma Pereira Junior
glaucius@gmail.com