Port Forwarding

After reading the various posts on this site, I can not find an answer, so here is my dilema.

What I am trying to to :

Home Windows 98 PC (Using MS-VPN) via Internet via E-Smith to NT VPN Server.

I have tried adding the ipmasqadm lines below (these were on someones web site)

ipmasqadm portfw -a -P tcp -L E-Smith-External-IP 1723 -R Internal-Vpn-Server 1723
ipmasqadm portfw -a -P tcp -L E-Smith-External-IP 500 -R Internal-Vpn-Server 500
ipmasqadm portfw -a -P tcp -L Internal-Vpn-Server 1723 -R E-Smith-External-IP 1723
ipmasqadm portfw -a -P tcp -L Internal-Vpn-Server 500 -R E-Smith-External-IP 500

But nothing happens. (The clients can not communicate with the NT Server).

Is there something that I have missed ?

(It is the plain vanilla E-Smith Server).

Thanks in advance.

Geoff Bennion