[Openswan Users] Windows XP L2TP and NAT-T problem

[Peter Bosman]

I've got open swan, L2TP and PPP running and I can connect to my LAN
through my VPN gateway over the net, as long as I'm not behind a nat box
on the client side. There seem to be some issues regarding transport
mode and NAT-t. I've also tried installing openswan 2.4 with the
KLIPS-2.6 module. This resulted in the same problem.
If I check my logs I can see a connection is brought up between the
client and the server in transport mode. They also switch to port 4500,
but the connection keeps being treated as a connection between the
NAT-box on the client side and the VPN server. There is no tunneling
through the NAT-box and no sign of the internal IP of the client behind
the NAT box in any of my logs.

Thanks for the help,

Peter Bosman
OSSO
pbosman at osso.nl