iftop is a command-line system monitor

System monitor

A system monitor is a hardware- or software- based system used to monitor resources and performance in a computer system.Software monitors occur more commonly, sometimes as a part of a widget engine. These monitoring systems are often used to keep track of system resources, such as CPU usage and...

tool that produces a frequently-updated list of network connections. By default, the connections are ordered by bandwidth usage, with only the "top" bandwidth consumers shown.

The iftop website gives the following description: 'iftop does for network usage what top(1) does for CPU usage. It listens to network traffic on a named interface and displays a table of current bandwidth usage by pairs of hosts. Handy for answering the question "why is our ADSL link so slow?".'

Options

Some options to iftop are listed below.

   -h                  display this message

   -n                  don't do hostname lookups

   -N                  don't convert port numbers to services

   -p                  run in promiscuous mode (show traffic between other

                       hosts on the same network segment)

   -b                  don't display a bar graph of traffic

   -B                  Display bandwidth in bytes

   -i interface        listen on named interface

   -f filter code      use filter code to select packets to count

                       (default: none, but only IP packets are counted)

   -F net/mask         show traffic flows in/out of network

   -P                  show ports as well as hosts

   -m limit            sets the upper limit for the bandwidth scale

   -c config file      specifies an alternative configuration file