iftop : bandwidth monitoring tool

'iftop' is a great tool for monitoring Bandwidth usage. Like the classic process monitoring tool 'top' it allows you to monitor bandwidth usage by hosts. Iftop displays a table of current bandwidth usage by pairs of hosts and has many configuration options.

The hosts with the highest bandwidth usage data is at the top.

Installation

• On Linux Mint/Ubuntu the install is  

  $ sudo apt-get -y install iftop

Running the Tool

• Require root access :

$ sudo iftop 

•  Uses the first interface by default but can specify the interface

$ sudo iftop -i eth0 

• iftop looks up the hostnames associated with addresses it finds in packets. This can cause substantial traffic so can be good to disable

 $ sudo iftop -i eth0 -n

• Show ports as well as hosts

$ sudo iftop -i eth0 -n -P

• Don't convert port numbers to services e.g. 80 to http

$ sudo iftop -i eth0 -n -P -N

•  Display Bandwidth in Bytes

 $ sudo iftop -i eth0 -n -P -N


Statistics Explained

• Statistics output above from left to right is for data rate (both sent and received) for the last
• 2 seconds
• 10 seconds
• 40 seconds

• Cumulative and peak data above displays
• Received
• Transmitted
• Total