CCNA Switching and Network Access Practice Question
Network Topology
You are connected to switch SW1. The network uses Rapid-PVST+ and SW1 has been accidentally configured with a low spanning-tree priority, causing it to become the root bridge for VLAN 10 even though it should not be. Additionally, an edge port connected to a server is repeatedly receiving BPDUs, causing it to go into err-disabled state. Configure SW1 so that it is never the root bridge for VLAN 10, and configure the edge port so that it automatically recovers from err-disabled state after 300 seconds. Finally, verify that SW1 is not the root bridge for VLAN 10.
⚠ Common exam trap
Students often confuse the priority values: lower priority is better to become root. To prevent a switch from becoming root, set its priority higher than the current root's. Also, remember that 'root secondary' sets a low priority (28672) and does not prevent root election. For errdisable recovery, use the specific cause (bpduguard) rather than 'all'.
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
✓
spanning-tree vlan 10 priority 36864; errdisable recovery cause bpduguard; errdisable recovery interval 300; show spanning-tree vlan 10
The issue is that SW1 has the spanning-tree priority for VLAN 10 set to 4096, which makes it the root bridge. To prevent this, you must set the priority higher than the current root bridge's priority (e.g., 32768 or higher). Additionally, the edge port (G0/1) is in err-disabled state because it received a BPDU while PortFast was enabled (BPDU Guard triggered). To automatically recover from err-disabled, you need to configure errdisable recovery cause bpduguard and set the interval to 300 seconds. After configuration, verify with 'show spanning-tree vlan 10' that SW1 is no longer the root and 'show errdisable recovery' to confirm the recovery settings.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
spanning-tree vlan 10 priority 36864; errdisable recovery cause bpduguard; errdisable recovery interval 300; show spanning-tree vlan 10
Why this is correct
Setting the priority to 36864 (or any value higher than the current root's priority) ensures SW1 will not become root for VLAN 10. The errdisable recovery commands enable automatic recovery from BPDU guard errdisable state after 300 seconds. The show command verifies SW1 is not the root.
- ✗
spanning-tree vlan 10 priority 4096; errdisable recovery cause bpduguard; errdisable recovery interval 300; show spanning-tree vlan 10
Why it's wrong here
Configuring `priority 4096` sets SW1's bridge priority to an extremely low value—lower than the default 32768 and likely lower than the current root—so SW1 will win the root election for VLAN 10 and become root immediately. While the BPDU guard recovery commands and `show spanning-tree vlan 10` verification are correct, they do not fix the underlying priority misconfiguration. The show command would actually confirm that SW1 is root, which is exactly the condition the task requires you to eliminate. To keep SW1 from ever becoming root, its priority must be higher than the current root's priority, such as 36864.
- ✗
spanning-tree vlan 10 root secondary; errdisable recovery cause bpduguard; errdisable recovery interval 300; show spanning-tree vlan 10
Why it's wrong here
This is incorrect because the 'root secondary' command sets the priority to 28672, which is still low enough to become root if the primary fails, but the question requires that SW1 never be root. Also, 'root secondary' does not guarantee it will never be root.
- ✗
spanning-tree vlan 10 priority 32768; errdisable recovery cause all; errdisable recovery interval 300; show spanning-tree vlan 10
Why it's wrong here
This is incorrect because 'errdisable recovery cause all' enables recovery for all errdisable causes, which is not specific to BPDU guard and may be too broad. The question specifically requires recovery from BPDU guard errdisable.
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.
✓spanning-tree vlan 10 priority 36864; errdisable recovery cause bpduguard; errdisable recovery interval 300; show spanning-tree vlan 10Correct answer▾
Why this is correct
Setting the priority to 36864 (or any value higher than the current root's priority) ensures SW1 will not become root for VLAN 10. The errdisable recovery commands enable automatic recovery from BPDU guard errdisable state after 300 seconds. The show command verifies SW1 is not the root.
✗spanning-tree vlan 10 priority 4096; errdisable recovery cause bpduguard; errdisable recovery interval 300; show spanning-tree vlan 10Wrong answer — click to see why▾
Why this is wrong here
The priority 4096 is too low and would still result in SW1 being the root bridge.
Why candidates choose this
Candidates might think that since 4096 is the default for some switches, it is acceptable, but the goal is to prevent SW1 from becoming root, so a higher priority is needed.
✗spanning-tree vlan 10 root secondary; errdisable recovery cause bpduguard; errdisable recovery interval 300; show spanning-tree vlan 10Wrong answer — click to see why▾
Why this is wrong here
The 'root secondary' command does not prevent the switch from becoming root; it only makes it the backup root.
Why candidates choose this
Candidates may confuse 'root secondary' with a command that prevents root selection, but it actually sets a low priority for failover.
✗spanning-tree vlan 10 priority 32768; errdisable recovery cause all; errdisable recovery interval 300; show spanning-tree vlan 10Wrong answer — click to see why▾
Why this is wrong here
Using 'cause all' is not the best practice; the requirement is to recover from bpduguard specifically.
Why candidates choose this
Candidates might think 'cause all' is acceptable because it includes bpduguard, but it is not the precise configuration asked for.
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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Related to this question
Learn chapter
Configuring Switch Ports for Desktops, VoIP Phones, APs, IoT, and Virtualized Hosts
Key term
Switch
A switch is a networking device that connects devices on a local area network and uses MAC addresses to forward data only to the intended recipient.
Key term
Bridge Protocol Data Unit
A Bridge Protocol Data Unit (BPDU) is a special message that network switches exchange to detect and prevent loops in an Ethernet network.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-301 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-301 exam.