How to use Tcpdump with examples for administrators

     tcpdump is a most powerful and widely used command-line packets sniffer or package analyzer tool which is used to capture or filter TCP/IP packets that received or transferred over a network on a specific interface. It is available under most of the Linux/Unix based operating systems. tcpdump also gives us a option to save captured packets in a file for future analysis.

See the list of interfaces on which tcpdump can listen:

Listen on interface eth0:

Listen on any available interface (cannot be done in promiscuous mode. Requires Linux kernel 2.2 or greater):

Be verbose while capturing packets:

Be more verbose while capturing packets:

Be very verbose while capturing packets:

Be verbose and print the data of each packet in both hex and ASCII, excluding the link level header:

Be verbose and print the data of each packet in both hex and ASCII, also including the link level header:

Be less verbose (than the default) while capturing packets:

Limit the capture to 100 packets:

Record the packet capture to a file called capture.cap:

Record the packet capture to a file called capture.cap but display on-screen how many packets have been captured in real-time:

Display the packets of a file called capture.cap:

Display the packets using maximum detail of a file called capture.cap:

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Display IP addresses and port numbers instead of domain and service names when capturing packets (note: on some systems you need to specify -nn to display port numbers):

Capture any packets where the destination host is 180.168.1.1 Display IP addresses and port numbers:

Capture any packets where the source host is 180.168.1.1 Display IP addresses and port numbers:

Capture any packets where the source or destination host is 180.168.1.1. Display IP addresses and port numbers:

Capture any packets where the destination network is 180.168.1.0/24. Display IP addresses and port numbers:

Capture any packets where the source network is 180.168.1.0/24. Display IP addresses and port numbers:

Capture any packets where the source or destination network is 180.168.1.0/24. Display IP addresses and port numbers:

Capture any packets where the destination port is 23. Display IP addresses and port numbers:

Capture any packets where the destination port is is between 1 and 1023 inclusive. Display IP addresses and port numbers:

Capture only TCP packets where the destination port is is between 1 and 1023 inclusive. Display IP addresses and port numbers:

Capture only UDP packets where the destination port is is between 1 and 1023 inclusive. Display IP addresses and port numbers:

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Capture any packets with destination IP 180.168.1.1 and destination port 23. Display IP addresses and port numbers:

Capture any packets with destination IP 180.168.1.1 and destination port 80 or 443. Display IP addresses and port numbers:

Capture any ICMP packets:

Capture any ARP packets:

Capture either ICMP or ARP packets:

Capture any packets that are broadcast or multicast:

Capture 500 bytes of data for each packet rather than the default of 68 bytes:

Capture all bytes of data within the packet:

   

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