BitMeter OS is a free, open-source, bandwidth monitor that works on Windows, Linux and Mac OSX.
BitMeter OS keeps track of how much you use your internet/network connection, and allows you to view this information either via a web browser,
or by using the command line tools.

The Web Interface displays various graphs and charts that show how your internet/network connection has been used over time.

The Monitor pane displays a graph that updates once each second, showing you what’s happening with your connection right now:

DarkStat is a simple Packet Sniffing Network Bandwidth monitoring Tool forDebian and other Linux distributions. DarkStat gives simple web based output with nice graphs and statistics , it will automatically refreshed. Darkstat uses a very low footprint and the memory, CPU usage.

Step 1. Installation:

apt-get install darkstat

Step 2. How to use darkstat:

1. Running darkstat for eth0 :

darkstat -i eth0

NOTE: Now darkstat will start and run in background.

Step 3. View stats:

In your Browser type the address:

vnStat is a console-based network traffic monitor for Linux and BSD that keeps a log of network traffic for the selected interface(s). It uses the network interface statistics provided by the kernel as information source. This means that vnStat won’t actually be sniffing any traffic and also ensures light use of system resources.

Step 1. Installation:

apt-get install vnstat

Step 2. Select the interface you wish to monitor:

for eth0 :

vnstat -u -i eth0

Repeat this changing eth0 for each interface you wish to monitor.

NOTE: Once the text database have been initialised you’re ready to monitor your bandwidth usage. The package installs a cronjob which will update the database every five minutes.

Cacti is a complete network graphing solution designed to harness the power of RRDTool’s data storage and graphing functionality. Cacti provides a fast poller, advanced graph templating, multiple data acquisition methods, and user management features out of the box. All of this is wrapped in an intuitive, easy to use interface that makes sense for LAN-sized installations up to complex networks with hundreds of devices.