==============
                                The TINC HOWTO
                                ==============

                                Wessel Dankers
                               wsl@nl.linux.org

Introduction
------------
Tinc is a system to create a virtual ethernet network on top of an existing
infrastructure. This infrastructure can be anything from modem lines to
gigabit ethernet networks, as long as they talk IP. Once you install and
configure tinc, your host will get an extra IP address, just like it would
when you stick an extra ethernet card into it. Using this IP address, it can
communicate with all hosts in its virtual network using strong encryption.

If you install Tinc on a router (and pick your numbers correctly) you can
have the router forward all packets. This way you can---instead of
connecting hosts---connect entire sites together! Now you need only one
outgoing network connection for both internet and intranet.

Getting Tinc
------------
Before you fetch the latest tarball, you might want to check if there's a
package for your Linux distribution. One of the main authors is a Debian
Developer, so you can expect the Debian packages to be very up to date.

The official website for Tinc can be found at http://tinc.nl.linux.org/.
There you can find Debian packages, RPM's and of course... the tarball!
Since we run Doohickey Linux Pro 1.0, for which no package exists (or
indeed the distribution itself) we shall compile the package ourselves.

Building
--------
The Tinc source adheres to so many standards it makes you head spin.
Even the debug messages have been localized! Amazing. Tinc also comes
with a configuration script. If you like to see what is there to
configure run ./configure --help | more. If you don't have time for such
nonsense:

	./configure --sysconfdir=/etc

This will see if your system is nice enough to run tinc on, and will
create some Makefiles and other stuff which will together build tinc.

	make
	make install

The first will do the actual build, the second copies all files into place.

The kernel
----------
FIXME

Configuring
-----------
The first thing we should do is pick network numbers. Tinc has a very
peculiar taste for network numbers, which is caused by the way it routes
traffic. However, it turns out to be really handy if you want to use
your tinc host as a router for a site.

The numbers have to be in a range that is not yet in use in your existing,
real network! In this example we will use numbers from the 192.168.0/16
range. This is standard CIDR notation for all IP addresses from 192.168.0.0
to 192.168.255.255. The /16 means that the first 16 bits form the network
part.

In the example we will connect three machines: f00f, fdiv and hlt. We will
give each an address, but not just that, also a slice of our address space
to play with.

      Host          Real address           Tinc network
      ---------------------------------------------------
      f00f          126.202.37.20          192.168.1.1/24
      fdiv          126.202.37.81          192.168.2.1/24
      hlt           103.22.1.218           192.168.3.1/24

It is very important that none of the Tinc netmasks overlap! Note how the
192.168.0/16 network covers the entire address space of the three hosts.
We will refer to the 192.168.0/16 network as the `umbrella' from now on.
As you can see we can fit 256 hosts into this umbrella this way, which is
also the practical maximum for tinc.

Let's create a configuration file for f00f. We have to put it in /etc/tinc,
unless you participate in multiple umbrella's (more on that later).