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Every time you open a webpage on your computer, data packets are sent and received on your network interface. Sometimes, analyzing these packets becomes important for many reasons. Thankfully, Linux offers a command line utility that dumps information related to these data packets in output.<\/p>\n
In this article, we will discuss the basics of the tool in question – tcpdump. But before we do that, it’s worth mentioning that all examples here have been tested on an Ubuntu 18.04 LTS machine.<\/p>\n
The tcpdump command in Linux lets you dump traffic on a network. Following is its syntax in short:<\/p>\n
tcpdump [OPTIONS]<\/p>\n
Here’s the detailed syntax:<\/p>\n
tcpdump [ -AbdDefhHIJKlLnNOpqStuUvxX# ] [ -B buffer_size ]
\n[ -c count ]
\n[ -C file_size ] [ -G rotate_seconds ] [ -F file ]
\n[ -i interface ] [ -j tstamp_type ] [ -m module ] [ -M secret ]
\n[ –number ] [ -Q in|out|inout ]
\n[ -r file ] [ -V file ] [ -s snaplen ] [ -T type ] [ -w file ]
\n[ -W filecount ]
\n[ -E spi@ipaddr algo:secret,… ]
\n[ -y datalinktype ] [ -z postrotate-command ] [ -Z user ]
\n[ –time-stamp-precision=tstamp_precision ]
\n[ –immediate-mode ] [ –version ]
\n[ expression ]<\/p>\n