Chapter 5. GRE and other tunnels

Table of Contents
5.1. A few general remarks about tunnels:
5.2. IP in IP tunneling
5.3. GRE tunneling
5.3.1. IPv4 Tunneling
5.3.2. IPv6 Tunneling
5.4. Userland tunnels

There are 3 kinds of tunnels in Linux. There's IP in IP tunneling, GRE tunneling and tunnels that live outside the kernel (like, for example PPTP).