welcome to LQ!
this is a nice iptables tutorial: http://iptables-tutorial.frozentux.n...-tutorial.html
as for the VPN thing, have you tried searching LQ to see if there's any info here that would help you find the rules you need?? you can search LQ using google like this:
BTW, according to this
A PPTP VPN server requires TCP port 1723 forwarded to the VPN server, as well as the GRE protocol (protocol 47).
so i did a search
for "iptables 47 gre" here at LQ and the first result was:
the last post
on that thread seems to sum it all up:
Originally posted by stevesl here
VPN (in the simplified MicroS*ft rras 56-but encryption client sense) is IP protocol # 47 (or GRE) AND IP protocol TCP port 1723.
assume for simplicity: iptables -P FORWARD ACCEPT
echo ">>>--- setup nat VPN"
iptables -t nat -A PREROUTING -i <Public-IFace> -p gre -d <VPN-Public-IP> -j DNAT --to-destination <VPN-DMZ-IP>
iptables -t nat -A PREROUTING -i <Public-IFace> -p tcp --sport 1024:65535 -d <VPN-Public-IP> --dport 1723 -j DNAT --to-destination <VPN-DMZ-IP>
anyways, i've never done any VPN so i'm not sure about any of this...
but i saw you hadn't received any replies so i figured i'd help get the ball rolling...
... good luck...