Which command helps in system troubleshooting by monitoring network packets?

The command that assists in system troubleshooting by monitoring network packets is tcpdump. This powerful utility captures and displays the packets being transmitted or received over a network interface, allowing administrators and network engineers to analyze traffic patterns, diagnose network issues, and identify potential security breaches. By filtering and displaying the information, tcpdump enables users to focus on the specific types of traffic or protocols that are relevant to their troubleshooting efforts.

In contrast, while lsof lists open files and the processes that opened them, it does not specifically monitor network packets. The ping command is used to check the reachability of a host on a network and measures the round-trip time for messages sent, but it does not provide detailed packet analysis. Lastly, traceroute tracks the path that packets take to reach a destination, providing insight into network hops but not monitoring the packets themselves. Hence, tcpdump is the most appropriate tool for monitoring and troubleshooting network packet activity.