NETSTAT in Linux

NETSTAT (network statistics) is useful for tracking down network problems. Use NETSTAT to
troubleshoot incoming or outgoing packet errors or to verify the presence of needed routes.
If you type netstat at the MS-DOS prompt, you see the protocol used, the name and local
address of the computer, and any connected computers and their current state

Netstat –a Displays all connections and listening ports
Netstat –e Displays Ethernet statistics
Netstat -n Displays addresses and numbers in numerical format
Netstat -s Displays the statistics of TCP/IP protocols: TCP, UDP, and IP

usage: netstat [-anv] [-f address_family]
netstat [-g | -p | -s] [-n] [-f address_family] [-P protocol]
netstat -m
netstat -i [-I interface] [-an] [-f address_family] [interval]
netstat -r [-anv] [-f address_family]
netstat -M [-ns] [-f address_family]
netstat -D [-I interface] [-f address_family]