From hikaro.com
Iftop is a niffty little tool to help in helping to monitor Network Bandwith. Similar to top, it display the local and external host(s) that are responsible for the most traffic activities.
There are some basic requirement first. Make sure you install
1. libpcap and libpcap-devel
2. ncurses and ncurses-devel
To install iftop you need to have EPEL repository configured first. To enable EPEL for CentOS 5 For 32-bits
rpm -Uvh http://download.fedora.redhat.com/pub/epel/5/i386/epel-release-5-3.noarch.rpm
and for 64-bits
rpm -Uvh http://download.fedora.redhat.com/pub/epel/5/x86_64/epel-release-5-3.noarch.rpm
To enable EPEL for CentOS 4 for 32-bits
rpm-Uvh http://download.fedora.redhat.com/pub/epel/4/i386/epel-release-4-9.noarch.rpm
and for 64-bits
rpm-Uvh http://download.fedora.redhat.com/pub/epel/4/x86_64/epel-release-4-9.noarch.rpm
now begin to install iftop
yum install iftop
To run iftop, simply run
iftop -i eth0
For iftop options, visit http://linux.die.net/man/8/iftop
