tcpdump Became My First Tool Before Wireshark
On a headless Linux box, tcpdump was faster than moving captures around blindly. A narrow capture at the right interface often answered the question immediately.
tcpdump
tcpdump on a PBX Taught Me to Trust the Wire Before the GUI
On a headless PBX, a narrow tcpdump capture often answered the important question faster than a full GUI trace: did the signaling or media packet actually reach the server?