Want to find what is using all of your bandwidth on Linux server? Try iftop tool. This command listens to network traffic on a given interface (such as eth0 or eth1), and shows a table of current bandwidth usage by pairs of hosts. iftop must be run with sufficient permissions (usually as root user) to monitor all network traffic on the interface. You can monitor bandwidth usage in a real time on RHEL or CentOS Linux based server.