This is a fork of the Piwik plugin IntranetSubNetwork from http://dev.piwik.org/trac/ticket/1054. Changes since that version can be seen on https://github.com/pklaus/IntranetSubNetwork/compare/v0.2...HEAD.

I'm using the plugin to see how many visitors of my site were using IPv4 vs. IPv6. You can, however, use it to identify the number of users from your local network (Intranet) or from any other subnet.
This is done by assigning the network different names in the file IntranetSubNetwork.php (see the lines below #131). Here is an example that lets Piwik assign the network label Global IPv4 to any IPv4 visitors:

<?php
if (Piwik_IP::isIpInRange($visitorInfo['location_ip'], array('0.0.0.0/0'))) { $networkName = 'Global IPv4'; }
?>

1. Create the folder ./IntranetSubNetwork in the plugins folder of your Piwik installation.
   Then copy the plugin files into that folder.
2. (optional) Adopt the networks defined in IntranetSubNetwork.php to your needs.
3. Activate the plugin on Piwik's settings page.
4. Add the Visitor Networks widget to your Piwik Dashboard.

If you know how to use Git, I recommend to install the plugin this way (makes it easier to keep it up to date):

cd /var/www/path/to/your/piwik/installation/plugins/
git clone git://github.com/pklaus/IntranetSubNetwork.git

If you had the original IntranetSubNetwork plugin (v0.2 by Alain) installed, you should be carefull about upgrading because I changed the name of the binary archive blob. This means that you have to discard the archive tables in your Piwik database when upgrading from this old version.