pppoe with NAT not working

[Sébastien Bernard]

Sébastien Bernard a écrit :

>Hi,
>I got a real big headache.
>
>My DSL provider a few ago upgraded my line and for this changed the BAS my
>box used to connect with.
>
>I had to reconfigure the ppp configuration.
>Before, I was using :
>pty "/usr/sbin/pppoe -I eth0 -T 80 -m 1452"
>It ceased working.
>
>The new configuration is using the rp-pppoe.so plugin as :
>plugin /usr/lib/pppd/2.4.3/rp-pppoe.so
>
>Since this modification, I'm not able to do any NAT or MASQUERADE with my
>gateway.
>My network architecture is :
>
>Private lan (192.168.x.x) => GW (public fixed address) => DSl Modem =>
>Internet
>
>When any machine on the private LAN try make a connection to an outside
>address, the connection made is ok.
>
>The three-way handshake is OK with the packets correctly NATED.
>
>When the outside peer tries to send data to the internal peer, the Gateway
>sends a reset back to it without breaking the connection inside of course.
>
>It looks like the netfilters didn't accept the incoming packets with
>payload as part of the nated connection.
>
>I had a look to the ip_conntrak connection and the faulty connection is
>correctly tracked, with an entry.
>
>I don't really understand what is happenning.
>
>The configuration is nothing special and could resumed as :
>iptables -t nat -A POSTROUTING -o ppp0 -j SNAT --to-source <public address>
>
>This was working before and I didn't touch anything to the configuration
>but the public address that changed when I moved to a speedier DSL line.
>
>If anyone could propose an explaination ...
>
>  Seb
>  
>
I figured out the problem.

NAT is not working with the rp-pppoe.so plugin.
I moved back to the

pty "/usr/sbin/pppoe -I eth0 -T 80 -m 1452"

Which worked now (go figure...).
And NAT is working again.

Any reason for this ?