ipsec tunnel with 2.6.0 kernel

[Nossie]

HI,

I have two networks protected by two NAT gateways/firewalls (both running Gentoo)
With the 2.4.x kernel I used FreeSwan to setup an encrypted tunnel between the two networks.

Now i've compiled the 2.6.0 kernel on both machines, and i'm trying to get the tunnel working again using the new ipsec code in the kernel and the Kame tools. I used the this HowTo to help me set it up.
I'm using Racoon with preshared keys as shown in the example.

When I start racoon, the logs tell me the tunnel is up (same messages as in the HowTo), but pinging from one network to the other doesn't work.

Is it possible to setup a tunnel this way (with kernel 2.6.0 and the Kame tools) when the gateway also act as a NAT gateway for the networks behind it ?
I didn't have any troubles with FreeSwan.

setup :