Tcpdump commands and usage examples

 

In most cases you will need root permission to be able to capture packets on an interface.

Using tcpdump (with root) to capture the packets and saving them to a file to analyze with Wireshark (using a regular account) is recommended over using Wireshark with a root account to capture packets on an “untrusted” interface.

See the Wireshark security advisories for reasons why.

 

See the list of interfaces on which tcpdump can listen:
tcpdump -D

Listen on interface eth0:
tcpdump -i eth0

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

Be verbose while capturing packets:
tcpdump -v

Be more verbose while capturing packets:
tcpdump -vv

Be very verbose while capturing packets:
tcpdump -vvv

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

Limit the capture to 100 packets:
tcpdump -c 100

Record the packet capture to a file called capture.cap:
tcpdump -w 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:
tcpdump -v -w capture.cap

Display the packets of a file called capture.cap:
tcpdump -r capture.cap

Display the packets using maximum detail of a file called capture.cap:
tcpdump -vvv -r capture.cap

Display IP addresses and port numbers instead of domain and service names when capturing packets:
tcpdump -n

Capture any packets where the destination host is 192.168.1.1. Display IP addresses and port numbers:
tcpdump -n dst host 192.168.1.1

Capture any packets where the source host is 192.168.1.1. Display IP addresses and port numbers:
tcpdump -n src host 192.168.1.1

Capture any packets where the source or destination host is 192.168.1.1. Display IP addresses and port numbers:
tcpdump -n host 192.168.1.1

Capture any packets where the destination network is 192.168.1.0/24. Display IP addresses and port numbers:
tcpdump -n dst net 192.168.1.0/24

Capture any packets where the source network is 192.168.1.0/24. Display IP addresses and port numbers:
tcpdump -n src net 192.168.1.0/24

Capture any packets where the source or destination network is 192.168.1.0/24. Display IP addresses and port numbers:
tcpdump -n net 192.168.1.0/24

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

Capture any packets where the destination port is is between 1 and 1023 inclusive. Display IP addresses and port numbers:
tcpdump -n dst portrange 1-1023

Capture only TCP packets where the destination port is is between 1 and 1023 inclusive. Display IP addresses and port numbers:
tcpdump -n tcp dst portrange 1-1023

Capture only UDP packets where the destination port is is between 1 and 1023 inclusive. Display IP addresses and port numbers:
tcpdump -n udp dst portrange 1-1023

Capture any packets with destination IP 192.168.1.1 and destination port 23. Display IP addresses and port numbers:
tcpdump -n “dst host 192.168.1.1 and dst port 23”

Capture any packets with destination IP 192.168.1.1 and destination port 80 or 443. Display IP addresses and port numbers:
tcpdump -n “dst host 192.168.1.1 and (dst port 80 or dst port 443)”

Capture any ICMP packets:
tcpdump -v icmp

Capture any ARP packets:
tcpdump -v arp

Capture either ICMP or ARP packets:
tcpdump -v “icmp or arp”

Capture any packets that are broadcast or multicast:
tcpdump -n “broadcast or multicast”

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

Capture all bytes of data within the packet:
tcpdump -s 0

 

Credit: rationallyparanoid

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