Cisco ENCOR Practice Exam 2025 – All-in-One Comprehensive Guide to Mastering Enterprise Network Core Technologies!

The correct answer is 15 seconds. In the context of the Spanning Tree Protocol (STP), when a switch receives a Topology Change Notification (TCN) Bridge Protocol Data Unit (BPDU), it initiates a process to update its MAC address table. The switch will then begin aging out entries that have not communicated in a 15-second time frame.

This 15-second aging period is aligned with the protocol's design to ensure that network topology changes do not lead to outdated MAC address information lingering in the switch's memory. By aging out these entries relatively quickly after a topology change, the network improves its ability to adapt to new configurations, thereby reducing the potential for traffic misdirection.

The specified time ensures that network resources are efficiently utilized, particularly in dynamic environments where devices may frequently connect and disconnect or where the topology is less stable. This mechanism ultimately enhances the overall performance and reliability of the network.