Linux kernel 2.4.x and IPSEC masquerade

From: Olivier Roset (oroset_at_free.fr)
Date: 05/31/05 

Date: Tue, 31 May 2005 14:58:22 +0200

Hi.

First, sorry for my english, but it's not my first language.

My problem is this :

I have a router/firewall who is running on a x86 box under linux redhat
7.2, with kernel 2.4.19.
The router is doing traffic masquerade and nat.

Behind this router/firewall, I have a lot of pc stations running windows xp.

I want to run checkpoint VPN-1 on some of this machines to connect to a
VPN server somewhere on the internet.
This software can use ipsec/ike to connect to this VPN server.

How can i (simply or not) masquerade the IPSEC traffic on the
router/firewall ?

Do I have to upgrade my linux kernel or install a third party software
on the router/firewall ???

Thanks for your help.

Olivier.