CCNA Switching and Network Access Practice Question
Which TWO statements correctly describe the behavior of Rapid PVST+ in a Layer 2 network?
⚠ Common exam trap
Cisco often tests the distinction between PVST+ (802.1D-based) and Rapid PVST+ (802.1w-based), and the trap here is assuming Rapid PVST+ still relies on timer-based convergence like standard 802.1D, when in fact it uses the faster RSTP handshake mechanism.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Rapid PVST+ runs a separate instance of RSTP for each VLAN.
Rapid PVST+ runs a separate instance of RSTP (802.1w) for each VLAN, enabling per-VLAN rapid convergence and load balancing. Option D is correct because PortFast allows access ports to transition to forwarding immediately, while BPDU Guard prevents loops by disabling a port that receives a BPDU. Option B is incorrect because Rapid PVST+ uses RSTP's handshake mechanism, not timer-based convergence like 802.1D. Option C is wrong: Rapid PVST+ is based on 802.1w, not 802.1D. Option E is false because Rapid PVST+ does not use 802.1Q to reduce instances; it maintains a separate spanning-tree instance per VLAN.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Rapid PVST+ runs a separate instance of RSTP for each VLAN.
Why this is correct
Rapid PVST+ creates a logical RSTP instance for every active VLAN, meaning each VLAN has its own bridge ID, root bridge election, and set of port roles. This per-VLAN separation lets a network engineer assign different root bridges per VLAN, enabling load balancing where traffic for different VLANs follows different spanning-tree paths. The underlying algorithm is 802.1w RSTP, not 802.1D, and because instances are separate, a topology change in one VLAN does not force a reconvergence in other VLANs.
- ✗
Rapid PVST+ is an enhancement of PVST+ and uses the same timer-based convergence as standard 802.1D.
Why it's wrong here
Rapid PVST+ is indeed an enhancement of PVST+, but it does not inherit 802.1D's timer-driven convergence. Instead, it adopts the RSTP (802.1w) mechanism, where switches exchange proposal/agreement messages, actively synchronize port roles, and can transition a designated port to forwarding almost immediately. Standard 802.1D depends on max_age and forward_delay timers, which typically take 30–50 seconds to converge; Rapid PVST+ avoids those delays by using an explicit handshake and a better understanding of edge and point-to-point links.
- ✗
Rapid PVST+ uses the 802.1D standard to compute the spanning tree for each VLAN.
Why it's wrong here
This statement is incorrect because Rapid PVST+ computes its spanning tree using 802.1w (RSTP), not the original 802.1D standard. While 802.1D uses port states such as blocking, listening, and learning plus long timers, RSTP introduces alternate and backup port roles, enables rapid transitions on designated and root ports, and uses a proposal/agreement handshake. The per-VLAN operation refers to running a separate RSTP instance per VLAN, but the protocol that computes each tree is fundamentally 802.1w, not 802.1D.
- ✓
PortFast and BPDU Guard are commonly configured on access ports to prevent loops and speed up convergence.
Why this is correct
PortFast allows an access port to transition directly to forwarding state, bypassing listening and learning. BPDU Guard disables the port if a BPDU is received, protecting against accidental loops from misconfigured devices. Together, they secure edge ports.
- ✗
Rapid PVST+ uses the 802.1Q trunking protocol to reduce the number of spanning-tree instances.
Why it's wrong here
Rapid PVST+ does not reduce the number of STP instances; it actually maintains per-VLAN instances. 802.1Q is a trunking protocol, but it does not affect the number of STP instances. Rapid PVST+ runs one instance per VLAN regardless of trunking method.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓Rapid PVST+ runs a separate instance of RSTP for each VLAN.Correct answer▾
Why this is correct
Rapid PVST+ creates a logical RSTP instance for every active VLAN, meaning each VLAN has its own bridge ID, root bridge election, and set of port roles. This per-VLAN separation lets a network engineer assign different root bridges per VLAN, enabling load balancing where traffic for different VLANs follows different spanning-tree paths. The underlying algorithm is 802.1w RSTP, not 802.1D, and because instances are separate, a topology change in one VLAN does not force a reconvergence in other VLANs.
✗Rapid PVST+ is an enhancement of PVST+ and uses the same timer-based convergence as standard 802.1D.Wrong answer — click to see why▾
Why this is wrong here
Rapid PVST+ is based on RSTP (802.1w), which uses a proposal/agreement handshake for fast convergence, not the timer-based convergence of 802.1D. PVST+ uses 802.1D timers, but Rapid PVST+ does not.
Why candidates choose this
Students may confuse Rapid PVST+ with PVST+, assuming both use the same convergence mechanism, or they may think that 'Rapid' only implies faster timers rather than a fundamentally different protocol.
✗Rapid PVST+ uses the 802.1D standard to compute the spanning tree for each VLAN.Wrong answer — click to see why▾
Why this is wrong here
Rapid PVST+ uses 802.1w (RSTP) for spanning tree computation, not 802.1D. 802.1D is the original STP standard with slower convergence and different port states.
Why candidates choose this
Since Rapid PVST+ is a per-VLAN implementation, some may incorrectly assume it still uses the older 802.1D standard, especially if they are not familiar with RSTP enhancements.
✗Rapid PVST+ uses the 802.1Q trunking protocol to reduce the number of spanning-tree instances.Wrong answer — click to see why▾
Why this is wrong here
Rapid PVST+ does not reduce the number of spanning-tree instances; it maintains one instance per VLAN. 802.1Q is a trunking protocol that does not affect the number of STP instances. Rapid PVST+ runs per-VLAN instances regardless of trunking method.
Why candidates choose this
Some may think that using 802.1Q trunking reduces STP instances because it is associated with VLAN tagging, but Rapid PVST+ actually increases instances compared to MSTP, which can group VLANs.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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Configuring Switch Ports for Desktops, VoIP Phones, APs, IoT, and Virtualized Hosts
Key term
Rapid Spanning Tree Protocol
Rapid Spanning Tree Protocol (RSTP) is a network protocol that prevents loops in Ethernet networks by quickly recalculating the best path when a link fails.
Key term
802.1Q
802.1Q is the networking standard that allows multiple virtual LANs (VLANs) to share a single physical network link by tagging Ethernet frames with VLAN identification information.
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