Tcpdump

In this article, we will be talking about Tcpdump. Is it a good option when looking to keep analyze your network?

Overview

When technical administrators are trying to get rid of troubleshooting problems, they turn towards tcpdump. Put merely, tcpdump is identified as a utility for the command line, which allows users to carry out network traffic capture and analysis through a system. It is mostly utilized as an instrument of security and troubleshooting. Tcpdump, a formidable and versatile tool embedded with numerous options and filers, can be employed in various cases. Given its nature as a command-line tool, it is safer and advised to run on remote servers or devices without a GUI, in other to collect data that will later be analyzed. Using a tool like cron, it can also be launched in the background. 

Linux Distributed

Tcpdump is always included with almost every Linux distributions, providing a high chance that it is already installed on every Linux user system. A library for network packet capture known as libpcap is required for tcpdump, without the installation of libpcap, the program will be automatically added as a dependency. Elevated permissions are required to capture packets for troubleshooting or analysis using tcpdump. 

Using Tcpdump

When capturing packets using tcpdump, this process gets interrupted when it receives an interrupt signal. Capturing can be interrupted by pressing ctrl+c, and the –c option limits the number of packets captured and stops tcpdump. Tcpdump is programmed by default ot resolve IP addresses and ports into names. In the course of network issues troubleshooting, using the IP addresses and port numbers is much easier; name resolution can be disabled by using the –n option, and port resolution can be disabled by using the –nn option. The capture and decoding of various protocols, including TCP, UDP, and ICMP, among others, is one of the capabilities of the tcpdump. 

Tcpdump is known for capturing large packets, some of which are mostly unrelated to the issues being troubleshot or dealt with at any point in time. A good example is when a connectivity issue with the webserver is undergoing the troubleshooting process. There is no need for SSH traffic, so the removal of SSH packets from the output will make the analysis of the real issue easier. The ability to filter captured packets using multiple parameters such as source, destination IP address, protocols, and ports is one of the attractive and prestigious features of tcpdump. I some cases, when using tcpdump, checking the packets’ header alone for information is all that is needed to troubleshoot a network issue.  Still in doubt? Learn more here as to why choose TCPDUMP.