Which type of information can be gathered using NetFlow?

NetFlow is a network protocol developed by Cisco for collecting IP traffic information. This protocol allows for the monitoring of network traffic flow and performance by gathering data on packet flows across the network. The primary focus of NetFlow is to capture detailed information about IP traffic flowing through a network interface, which includes aspects such as source and destination IP addresses, source and destination ports, protocols used, and the amount of data transferred.

By analyzing this flow data, network administrators can gain insights into network usage patterns, identify bandwidth hogs, monitor network performance, and troubleshoot network issues more effectively. This makes it a powerful tool for understanding IP network traffic details, which is why this option is correct.

Other choices, while they may pertain to network and system monitoring, do not align with the specific capabilities provided by NetFlow. System performance metrics, log authentication attempts, and error messages are typically gathered using different monitoring tools and protocols that focus on system health, user authentication events, and error logging, respectively.