If a device running STP receives an RSTP configuration BPDU, it discards the BPDU.

RSTP (IEEE 802.1w) is designed to be backward-compatible with legacy STP (IEEE 802.1D), but the reverse is not true. A legacy STP device only understands and processes STP BPDUs (Version 0). RSTP uses a newer BPDU format (Version 2) with a different BPDU Type field (0x02). When a device running only legacy STP receives an RSTP BPDU, it inspects the protocol version and BPDU type. Since the BPDU type is unrecognized by the STP protocol state machine, the STP device will discard the frame. This behavior is a key part of the interoperability mechanism between the two protocols.

B. False: The statement is true. An STP-only device cannot interpret the RSTP BPDU format and will drop the frame upon receipt, as specified by the protocol standards.

1. Huawei, "HCIA-Datacom V1.0 Training Material," document version C01, Chapter: "Spanning Tree Protocol," Section: "RSTP Interoperability with STP," p. 36. The material states, "An STP-enabled device discards RSTP BPDUs."

2. IEEE Std 802.1D-2004, "IEEE Standard for Local and metropolitan area networks - Media Access Control (MAC) Bridges," Clause 9.2.3, "Reception of BPDUs." This standard specifies that a bridge shall discard a received BPDU if the BPDU Type is not recognized. Legacy STP bridges only recognize Configuration (0x00) and TCN (0x80) BPDU types.