[pptp-server] howto access PPTP server behind a NAT server?

[Thies C. Arntzen]

    hi,
    (please cc:thies at thieso.net)

    i really hopt this is not a stupid question, i did do a quick
    google on my problem and haven't found a real answer - so,
    maybe somebody can help me

    my "dream" setup:

      
    pptp-server     <->     gateway   <-> *internet*  <-> me at home
    eth0:10.0.0.100)     eth1:10.0.0.1                    eth0:x.y.z.w
                         eth0:a.b.c.d

    the gateway runs linux 2.4.9 and does NAT the internal
    networt to the internet:
    
    iptables -t nat -s 10.0.0.0/24 -A POSTROUTING -o eth0 -j MASQUERADE

    i now want to forward all incoming pptp traffic from gateway
    to pptp-server so that me at home is on our internal network
    after login. i know that i have to forward port 1723 and
    protocol 43 somehow from gateway to pptp-server but i don't
    know how? i believe i need something like a reverse NAT from
    garteway to pptp-server - but i'm kinda clueless where to
    start.

    does somebody have an easy-enough solution that he/shw could
    share with me?

    regards,
    tc