What is Port Mirroring and How does a SPAN Port Work?
Your dashboard shows every interface green, the counters look clean, and the application owner still insists the network is dropping their transactions. Where do you look next? Availability data tells you a link is up. It cannot tell you what crossed that link or how long the server took to answer. Only the packets carry that, and port mirroring is how most engineers get a copy without cutting into a live cable.