Installation
sudo aptitude install ntop
sudo ntop -A
sudo /etc/init.d/ntop start
Now point your web browser at your server’s dns name (or IP) on port 3000.
Using ntop on a monitor port
Use the -o option to prevent NTOP from getting confused and shutting down if it sees it’s own mac address on the monitor port.
Start ntop with the following options
sudo ntop -u ntop -o -d
-u ntop will start the process under the ntop user.
-o starts ntop with no mac address. This options is the key for running on a monitor port.
-d starts ntop as a daemon so you can do other things on your system.</p>

To make ntop start at boot insert this into the file /etc/rc.local.

ntop -u ntop -o -d</div>