What command lists all of the open network connections on the system?

The command that lists all of the open network connections on the system is netstat. This command provides detailed information about network connections, routing tables, interface statistics, and much more. When executed with appropriate options, netstat can display active TCP and UDP connections, providing information such as the local and remote IP addresses, port numbers, and the state of the connections.

The other options serve different purposes. For instance, nmap is a network scanning tool primarily used for network discovery and security auditing. ifconfig is used for configuring and displaying network interface parameters, but it does not list active connections. Traceroute helps diagnose network routing issues by showing the path packets take to reach a destination host but does not display open connections. Therefore, netstat is the correct choice for the task of listing all open network connections.