What is the STP priority set to when configuring STP secondary root for a VLAN?

When configuring a Secondary Root Bridge for a VLAN in Spanning Tree Protocol (STP), the priority value is determined based on the default priority and the need to create a secondary path in the network topology. In STP, the default bridge priority is set to 32768. To configure a Secondary Root Bridge, an administrator typically sets a lower priority than the primary root to ensure it takes longer to become the root bridge, which helps maintain the desired hierarchy and path redundancy in the network.

In this case, the priority of 28672 is commonly used as it is a lower value than 32768, allowing the Secondary Root Bridge to have a higher preference over normal switches while still being lower than the primary root. This ensures that the primary root remains the preferred root bridge unless it becomes unavailable.

The choices related to other priority values such as 24576, 32768, and 40960 represent different configurations within STP, but among those listed, 28672 is specifically chosen for its relevance in setting a secondary root bridge, making it the correct answer in this context.