What happens if the boundary interface receives a superior VLAN 1 PVST+ BPDU but not sufficiently strong to become a root port (RP)?

When a boundary interface receives a superior VLAN 1 PVST+ BPDU that is not strong enough to establish it as a root port, the appropriate outcome is that the switch recognizes there is an inconsistency in the topology. This situation indicates that while there is a BPDU that is superior, some condition prevents the interface from taking on the role of a root port.

The switch's Spanning Tree Protocol (STP) mechanism is designed to maintain a loop-free topology by reacting to the information contained within BPDUs. In this case, the inability of the interface to become a root port due to inadequate strength of the BPDU results in the switch flagging this mismatch or inconsistency, thereby leading to the reporting of an inconsistency error. Thus, the interface remains in its current state without transitioning to either a forwarding state or becoming a designated port, which aligns with the principles of STP's operational procedures.

In contrast, accepting the BPDU and upgrading or transitioning the switch to a forwarding state would not accurately reflect the underlying issues introduced by the inadequate strength of the BPDU. Additionally, the scenario doesn’t support the interface turning into a root port, as per STP's functioning principles.