There are many tools that provide detailed statistics on network interfaces. Two very easily installed monitoring tools with great functions are ntop and Munin.
ntop monitors a network and may in some states be illegal because it creates detailed records of connections between IP addresses. Furthermore, it offers a nice browser GUI and does not need a running web server.The
ntop installs easily on Debian.
apt-get install ntop and choose the interface you want to monitor. After software installation, type
ntop -A and enter an administrator password for ntop's admin account. Now type
/etc/init.d/ntop start and point a browser to the
http://IP:3000 of this system (ntop is running on port 3000). You will get a feature-rich ...