Which Cisco STP mode extends on the IEEE 802.1w standard by providing an STP instance per VLAN?

Rapid PVST+ is an enhanced version of the traditional Spanning Tree Protocol (STP) that aligns with the IEEE 802.1w standard. The primary feature of Rapid PVST+ is its ability to create a separate Spanning Tree instance for each VLAN in a network. This capability allows for faster convergence times and improved network reliability by minimizing downtime during topology changes.

When a network experiences a change, such as a link failure or the addition of a new switch, Rapid PVST+ can rapidly reconfigure the STP for that specific VLAN instance without affecting the other active VLANs. The rapid transitions between states, achieved through features like the use of Proposal and Agreement messages, allows for convergence times that can be reduced to just a few seconds, which is a significant improvement over traditional STP methods.

This capability of providing an STP instance per VLAN not only enhances network performance but also allows for more granular control over Spanning Tree behavior within a multi-VLAN environment, making Rapid PVST+ an advantageous choice for network engineers managing complex networks.