Tcpdump prints out a description of the contents of packets on a network interface that match the boolean expression..

Examples:

• dns: $ tcpdump -i eth0 'udp port 53'
• http: $ tcpdump 'tcp port 80'
• ftp: $ tcpdump -i eth0 '(port 21 or 20)'

mtmtr combines the functionality of the traceroute and ping programs in a single network diagnostic tool.r combines the functionality of the traceroute and ping programs in a single network diagnostic tool.

iptraf is an ncurses-based IP LAN monitor GUI that generates various network statistics including TCP info, UDP counts, ICMP and OSPF information, Ethernet load info, node stats, IP checksum errors, and others…

iftop listens to network traffic on a named interface … and displays a table of current bandwidth usage by pairs of hosts.

-i interface

-p Run in promiscuous mode

-P Turn on port display

-F net/mask – Specifies a network for traffic analysis

iperf -c iperf.ovh.net -m -i 1 -t 10 -r