Using router as modem adsl under linux
I am trying to run a vpn application (freeswan), which requires to have the vpn/firewall/routing under the same machine, with a public external ip address.
Since I have a router (usr), I can't have this config as the router keeps the public ip. I am trying to run this router as a modem, but so far I have not been able to connect to the internet. Do I need any flag on the kernel or special config under linux to have this? or this is just a router config issue?
Thanks in advance,