You can override this default behaviour by specifying the count of packets you want to capture beforehand using the -c flag. While running the tcpdump command for the first time, you might notice that the system continues to capture network packets until you pass an interrupt signal. The last field ( length 33) contains the length of the overall packet captured by tcpdump. Generally, you will find two protocols- IP and IP6, where IP denotes IPV4 and IP6 is for IPV6. The fourth field includes information related to the network protocol name. In the snippet above, wlp0s20f3 is the name of the wireless interface and Out is the packet flow. The second and third fields denote the interface used and the flow of the packet. The time recorded is extracted from your system's local time. The first field ( 17:00:25.369138) displays the time stamp when your system sent or received the packet. The sequence number of data in the packet. The output contains the following information. Keep in mind that not all packets are captured this way, but this is the general format followed by most of them. Here's what the output of a single packet looks like. Starting from the third line, each line of the output denotes a specific packet captured by tcpdump. Related: What Is the Open Systems Interconnection Model? 2.
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