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

The command required to change the port ID for a VLAN primarily involves modifying the port priority settings in the spanning tree protocol. This is crucial because the port ID in spanning-tree configurations is determined by a combination of the port priority and the port number. By adjusting the port priority using the spanning-tree command, you effectively influence the port ID assignment based on the rules set by the Spanning Tree Protocol (STP).

Port IDs are particularly important as they are utilized by STP to prevent loops in a network by determining the root port and designated port for VLANs. The balancing act of using port priority allows for a more controlled selection of which ports should be active in the network for any given VLAN, based on their priority settings.

The other options don't provide the correct commands needed to alter the VLAN port ID effectively. For instance, the commands that start with "show" are typically used for displaying configuration and status rather than making changes. Any command that appears to focus on direct modification of the port-ID may not align with the proper syntax or method used within Cisco's command-line interface.