how to use netstat command and its examples

• About netstat : To print  network connections, routing tables, interface statistics, masquerade connections, and multicast memberships
• It comes from: “net-tools-1.60” package.
• Configuration Files:
         /etc/services — The services translation file
         /proc/net/dev — device information
         /proc/net/raw — raw socket information
         /proc/net/tcp — TCP socket information
         /proc/net/udp — UDP socket information
         /proc/net/igmp — IGMP multicast information
         /proc/net/unix — Unix domain socket information
         /proc/net/route — IP routing information
         /proc/net/snmp — Statistics
• Path: /bin/netstat

Examples:

1. To display the kernel routing table

$ netstat -r $ netstat –route

2. To display multicast group membership information

$ netstat -g $ netstat –groups

 3. To display the kernel interface table

$ netstat -i $ netstat –interfaces $ netstat –interfaces=eth0

4. To display a list of masqueraded connections

$ netstat -M $ netstat –masquerade

5. To display summary statistics of each protocol

$ netstat -s $ netstat –statistics

6. To set to verbose 

$ netstat -v $ netstat –verbose

7. To show numerical addresses instead of trying to determine symbolic host

$ netstat -n $ netstat –numeric

8. To numerical host addresses but does not affect the resolution 

$ netstat –numeric-hosts

 9. To numerical port numbers but does not affect the resolution

$ netstat –numeric-ports

10. To show numerical user IDs but does not affect the resolution

$ netstat –numeric-users

 11. To print the selected information every second continuously

$ netstat -c  $ netstat –continuous

12. To display the additional information

$ netstat -e $ netstat –extend

13. To include information related to networking timers

$ netstat -o $ netstat –timers

14. To show the PID and name of the program to which each socket belongs

$ netstat -p $ netstat –program

15. To show only listening sockets

$ netstat -l $ netstat –listening

16. To show both listening and non-listening sockets

$ netstat -a $ netstat –all

17. To print routing information from the FIB

$ netstat -F

 18. To print routing information from the route cache

$ netstat -C

19. To print SELinux context

$ netstat -Z $ netstat –context

20. To stop trimming long addresses

$ netstat -T $ netstat –notrim

21. To set delay

$ netstat delay 2

 22. To get the help

$ netstat -h $ netstat –help

 23. To get the version

$ netstat –version

 Cocktail Examples

24. To see the currently active routing table

$ netstat -rnv

25. To see all the socket information

$ netstat -anp

26. To see all the listening ports

$ netstat -anp | grep LISTEN

27. To see all the process/services running and listening on ports

$ netstat -lnptu

28. To see the protocol specific statistics (e.g. for TCP)

$ netstat -pt

29. To see the interface activity stats 

$ netstat -i -t 2 $ netstat -it 2

30. To see the summary stat for a particular port

$ netstat -st               (For TCP) $ netstat -su               (For UDP)

Related Commands: ss, ip