A network engineer is examining a Rapid PVST+ topology. Switch SW3 has two paths toward the root bridge. On one interface (Gi0/1), SW3 has the lowest-cost path to the root and this port is forwarding. On a second interface (Gi0/2), SW3 receives superior BPDUs from a neighbor, but this port offers a higher-cost path to the root and is currently in the discarding state as a backup route to the root. What port role has RSTP assigned to Gi0/2?