In this article, we shall discuss the most original packet sniffer- tcpdump. By the end of the read, you will have obtained a more complex understanding of the analyzer and a more justified reason for its use.
All About TCPDUMP
Tcpdump is an open-source and command-line packet analysis tool. It comes pre-installed in most Unix operating systems and only works in these systems or similar-looking systems-Linux and MacOS. It is the most preferred analyzer by system admins because it is a command-run analyzer, and it, therefore, does not require a heavy-duty machine to run.
You can use tcpdump to capture data files in a network while on transit, analyze the packets, look for and troubleshoot any diagnostic problems. Much like the Wireshark analyzers, tcpdump captures all the data in a specified route and dump it on the screen for analysis. Once the analyzer renders the packets on the screen, you can apply the various filtering tools to break them down into manageable chunks.
Tcpdump is one of the oldest packet capturing utilities in the market. Here is a brief of its best features that makes it indisposable despite severe technological advancements.
Tcpdump analyzers are commonly executed via a command line. This feature allows it to be used in various cases, such as remote servers, without any graphical user interfaces. It can also be launched in the background using the nohup command that lets the analyzer even if the terminal it is launched from closes.
Tcpdump analyzers print the contents of their captured packets to the Boolean equivalent of the command rendered. These analyzers are able to also save these packets into a file instead of ‘dumping’ them on a screen. The saved files are then used later on for a further analysis on more powerful tools such as Wireshark.
There are two ways tcpdump analyzers do this;
Flagging the analyzer with the –w command saves it into a file instead of printing it. The –r later allows it to read from the saved packet as opposed to reading packets on the network interface card.
Limitations of TCPDUMP?
Cannot Read Pcap Files
For packet analyzers to work, they mostly rely on application programming interfaces (APIs)for packet capture. Windows operating systems use the libcap API, while Unix/Linux systems use the Pcap APIs. Tcpdump is more proficient with Linux/Unix systems, and for this reason, inasmuch as its analyzers will capture all data, it cannot read the pcap files it captures.
All is not lost, though; it is still possible to save these pcap packet files to another tool like Wireshark, for instance, for analysis.
Steep Learning Curve
Tcpdump, as we explained earlier, is a command-line run analyzer. That alone necessitates the need to master several commands to filter and segment data. This steepens its learning curve. Other than that, its interfaces are relatively simple to use and understand.
Tcpdump analyzers were initially developed to run and diagnose problems prevalent in TCP/IP networks. It only worked on Unix systems, but over time, its technologies have been improved to support Windows systems as well. Despite additional and more fierce features from its competitors, the tcpdump sniffers have retained their industry position for one reason- universality.
Tcpdump protocols can be employed in almost all systems available with little to no incompatibility limitations. Its superior competitors are often used alongside it, each complementing the other.Download