Question

An access switch running Rapid PVST+ has two uplinks: Gi1/0/1 (root port toward the primary distribution switch) and Gi1/0/2 (a discarding alternate port toward the secondary distribution switch). The primary distribution switch is powered down for maintenance. What happens to Gi1/0/2, and why is the convergence fast?

Accepted Answer

Gi1/0/2 transitions directly from discarding to forwarding as the new root port because RSTP already knew it as a backup path and can immediately promote the alternate port without waiting for timers.

Answer

Gi1/0/2 must first pass through the listening and learning states for the standard 30-second forward delay before it can forward traffic.

Answer

Gi1/0/2 remains discarding and the switch floods a topology change that forces every port in the VLAN to relearn MAC addresses before any uplink can forward.

Answer

Gi1/0/2 transitions to the designated role and begins sending superior BPDUs to elect itself as the new root bridge for the topology.