2007 Mar 14 - Wed

iftop: Display Bandwidth Usage on an Interface

iftop is an interesting command line utility for tracking traffic on an interface. tcpdump is good for looking at packet content in real time, this is good for looking at what makes up traffic bandwidth in realtime.

Installation is easy:

apt-get install iftop 

I have second interface on the monitoring server which is listening to what ever traffic passes in and out of the internal interface of the firewall. The switch port connecting to the firewall is 'span'd to the monitoring server's eth1. This allows one to monitor all components of inbound and outbound traffic.

Here is the command I used for looking at generating a bar chart of traffic details:

iftop -i eth1 -F 10.0.0.0/255.0.0.0 -P

The -F parameter provides an indication of what is internal traffic and what is external traffic. The -P parameter shows the ports in each flow. For run-time commands, take a look at 'man iftop'.