How a Switch in Rapid PVST+ Mode Responds to a Topology Change

D

Rapid PVST+This spanning-tree mode is the same as PVST+ except that is uses a rapid convergence based on the IEEE 802.1w standard. To provide rapid convergence, the rapid PVST+ immediately deletes dynamically learned MAC address entries on a per-port basis upon receiving a topology change. By contrast,

PVST+ uses a short aging time for dynamically learned MAC address entries.

The rapid PVST+ uses the same configuration as PVST+ (except where noted), and the switch needs only minimal extra configuration. The benefit of rapid PVST

+ is that you can migrate a large PVST+ install base to rapid PVST+ without having to learn the complexities of the MSTP configuration and without having to reprovision your network. In rapid-PVST+ mode, each VLAN runs its own spanning-tree instance up to the maximum supported.

Rapid PVST+ (Per-VLAN Spanning Tree) is a Cisco proprietary protocol that allows for multiple VLANs to have their own separate instance of Spanning Tree Protocol (STP) running on a single switch.

When a switch in rapid PVST+ mode detects a topology change, it immediately sends topology change notifications to its neighbors to inform them of the change.

Regarding the question, the correct answer is option C: "It sets a timer to delete dynamic MAC addresses that were learned by all ports on the switch."

This means that when a topology change occurs, the switch starts a timer to delete dynamic MAC addresses that were learned by all ports on the switch. The switch does not immediately delete the MAC addresses, but instead waits for the timer to expire. The default value for this timer is 300 seconds, but it can be adjusted using the "mac address-table aging-time" command.

This behavior is different from the standard STP, which clears the MAC addresses learned by all ports in the same STP instance immediately. By keeping the MAC addresses for a certain period, the switch can avoid unnecessary flooding of unknown unicast traffic, as the switch can still forward frames based on the learned MAC addresses until they expire from the table.

In summary, when a switch in rapid PVST+ mode detects a topology change, it sets a timer to delete dynamic MAC addresses that were learned by all ports on the switch. This behavior is designed to minimize the impact of the topology change on the network and avoid unnecessary flooding of unknown unicast traffic.