Google is showing me some returns on PPTP/GRE NAT through iptables/netfilter that will allow multiple connections.
However, I am not finding an example of using this pptp helper module that allows for this. Anyone done this before?
This changed radically in kernel 2.6.14, and that accounts for the various random documentation examples you're finding (many with the pre-2.6.14 syntax). I don't have a machine handy to test on, but you should be fine with loading
I am assuming you are talking about being behind a NAT, and trying to have multiple users connect to a remote VPN server, then I just managed to fix this on DD-WRT v24-sp2 (04/16/10):
Apparently the kernel modules were missing which do the NAT translation for the GRE protocol - inserting them proved enough. I have added the following lines to the firewall script:
The rest of iptables/netfilter is already set up correctly in DD-WRT apparently :)
If wanted I can dig up the rest of the NAT table entries relating to this.