A virtual network shared between multiple edge nodes in n2n is called a *community*. A single supernode can relay multiple communities and a single PC can be part of multiple communities at the same time. An encryption key can be used by the edge nodes to encrypt the packets within their community.
N2n tries to enstablish a direct P2P connection between the edge nodes when possible. When this is not possible (usually due to special NAT devices), the supernode is also used to relay the packets.
Some linux distributions already provide n2n as a package so a simple `sudo apt-get install n2n` will do the work. Alternatively, up to date packages for most distributions are available on [ntop repositories](http://packages.ntop.org/).
**IMPORTANT** It is strongly adviced to choose a custom community name (-c) and a secret encryption key (-k) in order to prevent other users to connect to your PC. For privacy and to reduce the above server load, it is also suggested to set up a custom supernode as exmplained below.
You can create your own infrastructure by setting up a supernode on a public server (e.g. a VPS). You just need to open a single port (1234 in the example below) on your firewall (usually iptables).
1. Install the n2n package
2. Edit `/etc/n2n/supernode.conf` and add the following:
```
-l=1234
```
3. Start the supernode service with `sudo systemctl start supernode`
Now the supernode service should be up and running on port 1234. On your edge nodes you can now specify `-l your_supernode_ip:1234` to use it. All the edge nodes must use the same supernode.
Routing the traffic
-------------------
On linux, n2n provides a standard TAP interface, so routing works gracefully via the standard system utilities as follows.
In this example host1 is the edge router (with n2n IP 192.168.100.1), whereas host2 is the client.
Here is how to configure host1:
1. Add the `-r` option to the edge options to enable routing
2. Enable packet forwarding with `sudo sysctl -w net.ipv4.ip_forward=1`
3. Possibly configure iptables to `ACCEPT` the packets on the `FORWARD` chain.
On host2, run the `edge` program as normal to join the host1 community.
In order to forward all the internet traffic via host2:
```sh
# Determine the current gateway (e.g. 192.168.1.1)
$ ip route show default
# Add a route to reach the supernode via such gateway
$ sudo ip route add supernode.ntop.org via 192.168.1.1
