Cisco Certified Network Professional 2025 – 400 Free Practice Questions to Pass the Exam

The command "monitor session session-number source vlan vlan-id" is used to define the source of mirrored traffic in a network environment where packet monitoring is necessary. By specifying a VLAN as the source, the command instructs the switch to capture and mirror all traffic that flows through the specified VLAN. This is especially useful for network analysis and troubleshooting, as it allows for the examination of traffic from multiple devices within that VLAN without needing to individually access each device.

Monitoring sessions are vital for network performance analysis and security assessments. While the other options relate to different network configurations — such as setting a destination for mirrored traffic, enabling trunking, or managing bridging — they do not pertain to the specific function of defining the source of traffic for monitoring purposes. Thus, the focus here is clearly on capturing and handling traffic from the designated VLAN to facilitate further analysis.