I have a Debian server with one static external IP. It has PPTP server installed. Local IP is 192.168.1.200 and remote IPs are 192.168.1.201-209. I have several users, who connect to my server using their routers through the Internet. VPN work flawlessly. Routers have UPnP enabled, but devices, that use UPnP, are reporting no UPnP available. What rules do I need in iptables to make it work? Thanks.