OpenRC/Stacked runlevel

This page documents a tutorial for setting up complicated networking with the help of stacked runlevel. Along the tutorial other tricked for OpenRC are also expected.

The short version is that

= senario = We have a university library which provides wireless network, with the following steps:
 * 1) associate with the AP with no authentication
 * 2) setup a PPTP VPN through NAT against an internal server
 * 3) using an HTTP proxy to access the websites

There are big advantages:
 * GRE protocol used by PPTP uses source ip to identify client, thus do not support tunneling through NAT. There is enhanced GRE for such perpose, but routers has different implementations and only considered PPTP clients for Microsoft Windows and Apple Mac OS X, not for Linux.