This article covers how to use the tcpdump command for troubleshooting and analyzing the network on your Linux system. tcpdump is the world's premier network analysis tool—combining both power and simplicity into a single command-line interface.
Basically, tcpdump is a valuable tool for anyone looking to get into networking or information security.
The raw way it interfaces with traffic, combined with the precision it offers in inspecting packets make it the best possible tool for learning TCP/IP.
Protocol Analyzers like Wireshark are great, but if you want to truly master packet-fu, you must become one with tcpdump first.