Bandwidth Monitoring Tools for FreeBSD and Linux: nload

Bandwidth in computer networking refers to the data rate supported by a network connection and it represents the capacity of the connection.
nload is a ncurse based network traffic analyser.

nload allow a system administrator to easily monitor the traffic going on its network. It provide both a graph of incoming and outgoing traffic as well as network data transfer statistics.
To install nload in CentOS, Fedora, RHEL ( make sure you have DAG repository enabled ):
# yum install nload
To install nload in FreeBSD:
# cd /usr/ports/net/nload
# make install clean
To install nload in Ubuntu/Debian:
# sudo apt-get install nload
Start nload by typing the following command:
# nload if
where if is the network interface.
Example:
# nload rl0