dump traffic on a network
-i Listen on interface. If unspecified, tcpdump searches the system interface list for the lowest
numbered, configured up interface (excluding loopback). Ties are broken by choosing the earliest
On Linux systems with 2.2 or later kernels, an interface argument of ``any'' can be used to
capture packets from all interfaces. Note that captures on the ``any'' device will not be done in
If the -D flag is supported, an interface number as printed by that flag can be used as the
-v When parsing and printing, produce (slightly more) verbose output. For example, the time to live,
identification, total length and options in an IP packet are printed. Also enables additional
packet integrity checks such as verifying the IP and ICMP header checksum.
When writing to a file with the -w option, report, every 10 seconds, the number of packets
-X When parsing and printing, in addition to printing the headers of each packet, print the data of
each packet (minus its link level header) in hex and ASCII. This is very handy for analysing new
-w Write the raw packets to file rather than parsing and printing them out. They can later be
printed with the -r option. Standard output is used if file is ``-''. See pcap-savefile(5) for a
description of the file format.
-C Before writing a raw packet to a savefile, check whether the file is currently larger than
file_size and, if so, close the current savefile and open a new one. Savefiles after the first
savefile will have the name specified with the -w flag, with a number after it, starting at 1 and
continuing upward. The units of file_size are millions of bytes (1,000,000 bytes, not 1,048,576
-G If specified, rotates the dump file specified with the -w option every rotate_seconds seconds.
Savefiles will have the name specified by -w which should include a time format as defined by
strftime(3). If no time format is specified, each new file will overwrite the previous.
If used in conjunction with the -C option, filenames will take the form of `file<count>'.
-W Used in conjunction with the -C option, this will limit the number of files created to the
specified number, and begin overwriting files from the beginning, thus creating a 'rotating'
buffer. In addition, it will name the files with enough leading 0s to support the maximum number
of files, allowing them to sort correctly.
Used in conjunction with the -G option, this will limit the number of rotated dump files that get
created, exiting with status 0 when reaching the limit. If used with -C as well, the behavior will
result in cyclical files per timeslice.