Introduction

iftop is a real good utility both for your own PC/Laptop and for your server and specially good for the latter and even better if this server is acting as the main router in your premises.

Well lets explain what iftop does, it is more or less like top, or htop but it does not measure the processes in the processor, but it measure the “processes” in the ethernet interface, giving you information about the IPs that have a connection with the PC where iftop is running, also giving information about the traffic, if it is incoming or outcoming, also how much traffic there is in that connection and the total amount of traffic in the interface.

Installation

Ubuntu / Debian

sudo aptitude install iftop

Fedora / CentOS

yum install iftop

Gentoo / Sabayon

emerge iftop

Some options

Some of the options I use the most are:

  • -p Enables promiscuous mode, so the traffic on any interface (if there is more than once) is checked and counted
  • -P Shows also the port that connection is using both on our side and on the other side
  • -N Do not resolve port names, which is the default behavior when you enable the -P option, so it will shows you :www or :80

Screenshot

iftop screenshot</img>