RSTP Configuration BPDU Type Field Value
Short answer
C The Type field in RSTP configuration BPDUs is 0x02, distinguishing them from legacy STP BPDUs which use 0x00.
Question
Key Takeaways
RSTP changes the Configuration BPDU Type from 0x00 (legacy STP) to 0x02 to ensure backward compatibility and clear identification.
The Type field in RSTP configuration BPDUs is 0x02. This distinguishes RSTP packets from legacy STP BPDUs, which use 0x00.
Common mistake: Selecting 0x00 (Option A) by confusing RSTP with legacy STP, where Configuration BPDUs have a Type of 0.
Expert Analysis
The question asks for the Type field value in RSTP configuration BPDUs. To answer this, one must distinguish between the legacy IEEE 802.1D STP and the faster IEEE 802.1w RSTP (and its extension MSTP).
Legacy STP vs. RSTP Type Values In classic STP, there are two BPDU types:
- Configuration BPDU: Type =
0x00(or 0) - TCN BPDU: Type =
0x01(or 1)
RSTP modifies these values to allow switches to identify RSTP-specific packets while maintaining backward compatibility with legacy STP devices.
- RSTP/MST Configuration BPDU: The Type field is set to
0x02(or 2). This is the primary BPDU used for topology synchronization and port role negotiation in RSTP. - TCN BPDU: Remains
0x01.
Analysis of Options
- Option A (
0x00) is incorrect because this value is reserved for legacy STP Configuration BPDUs. If an RSTP switch receives a BPDU with Type0x00, it treats the sender as a legacy STP device and falls back to STP behavior on that port. - Option B (
0x01) is incorrect because this is the Type value for Topology Change Notification (TCN) BPDUs in both STP and RSTP. - Option C (
0x02) is correct. It explicitly identifies the packet as an RSTP (or MST) Configuration BPDU. - Option D (
0x03) is not a standard BPDU type value in IEEE 802.1D/802.1w.
Why Option A is a Common Trap
The most attractive wrong answer is A (0x00). Candidates often memorize that "Configuration BPDUs have Type 0" based on legacy CCNA or older study materials. However, RSTP specifically changed this to 0x02 to differentiate itself. Confusing the legacy value with the RSTP value is a frequent error in certification exams focusing on network evolution.
Exam Strategy
When studying spanning tree protocols, always create a comparison table for BPDU types across STP, RSTP, and MSTP. Specifically, memorize that RSTP shifts the Configuration BPDU type from 0 to 2. During the exam, if you see 'RSTP' or 'MST', immediately look for '2' or '0x02' for configuration BPDUs, rather than defaulting to the legacy '0'.
Frequently Asked Questions
Why does RSTP change the BPDU Type to 0x02?
Does TCN BPDU Type change in RSTP?
Community Votes
75% of anonymous learners picked answer C. Votes are pick records left by other test-takers — they are not the verified answer.
Discussion 4 contributions
Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.
From public community threads 4
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Fmoura17 👍 1 Answered CThe correct answer is C. 0x02. The Type field in BPDU headers identifies the type of BPDU being sent: Type ValueBPDU Type0x00STP Configuration BPDU0x01TCN (Topology Change Notification) BPDU0x02RSTP/MST Configuration BPDU ✅ RSTP uses 0x02 in the Type field to identify its configuration BPDUs, which distinguishes them from legacy STP BPDUs (0x00).
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konyuz 👍 1 Answered CIn Classic STP, the Type field had a value of 0. RSTP changes this value to 2 to identify its own specialized BPDUs, known as RST BPDUs.
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Heidorn 👍 1 Answered AFor RSTP Configuration BPDUs, its actually 0x00
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deva666859 👍 1 Answered CRSTP IS 0x02
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