What happens if a BPDU is received on an interface with BPDU Guard enabled?

When BPDU Guard is enabled on an interface and a Bridge Protocol Data Unit (BPDU) is received, the interface is designed to protect the network from potential loop conditions caused by misconfigurations or malicious devices. In this scenario, the interface will go into error-disable mode as a safety measure.

This action is taken because BPDUs are typically not expected on port connections that are configured as edge ports or access ports, which should connect only to end devices rather than other switches. When BPDUs are detected on these interfaces, it indicates a possible violation of the intended design, possibly signaling a switch has been connected to a port configured for end devices. Error-disable mode effectively disables the port to prevent loops and other associated issues in the spanning tree topology.

The other options do not accurately reflect the behavior of BPDU Guard. The interface will not remain active, nor will BPDUs be processed in a manner that allows the network to re-converge. Instead, the primary purpose of BPDU Guard is to ensure the stability and integrity of the spanning tree by proactively disabling interfaces that shouldn't be participating in BPDU exchanges.