Quick Answer
The correct configuration to prevent a new switch from becoming the root bridge is to set its bridge priority to 61440. In RSTP and STP, the root bridge is elected based on the lowest bridge priority value, which must be a multiple of 4096; by assigning a high priority like 61440, you ensure the new switch’s numerical value is higher than that of the existing root bridge, so it will never assume the root role. On the Cisco DevNet Associate 200-901 exam, this question tests your understanding of spanning-tree topology control during network migrations, often appearing as a scenario where you must avoid topology disruption while adding redundant links. A common trap is confusing priority with cost or assuming a lower number is always safer—remember, lower priority wins root election, so a high priority like 61440 keeps the switch subordinate. Memory tip: think “61440 = high number, low chance of becoming root.”
This 200-901 practice question tests your understanding of network fundamentals. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
During a network migration, an engineer needs to replace a legacy core switch with a new one without disrupting the existing STP topology. The new switch supports RSTP and will be connected via two trunk links. Which configuration should be applied to the new switch to prevent it from becoming the root bridge?
Enable root guard on the trunk ports
Why wrong: Root guard protects against inferior BPDUs, does not prevent this switch from becoming root.
Configure the bridge priority to 61440
High priority makes it less likely to become root.
Enable BPDU guard on the trunk ports
Why wrong: BPDU guard disables ports if BPDU received, not related to root election.
Set the bridge priority to 0
Why wrong: Priority 0 makes it the root.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Configure the bridge priority to 61440
Option B is correct because setting the bridge priority to 61440 (which is a valid priority value in increments of 4096) ensures the new switch has a higher numerical priority than the current root bridge, preventing it from becoming the root. In STP/RSTP, the switch with the lowest bridge priority becomes the root bridge; by configuring a high priority, the new switch will not disrupt the existing topology.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Enable root guard on the trunk ports
Why it's wrong here
Root guard protects against inferior BPDUs, does not prevent this switch from becoming root.
Configure the bridge priority to 61440
Why this is correct
High priority makes it less likely to become root.
Related concept
Read the scenario before looking for a memorised answer.
Enable BPDU guard on the trunk ports
Why it's wrong here
BPDU guard disables ports if BPDU received, not related to root election.
Set the bridge priority to 0
Why it's wrong here
Priority 0 makes it the root.
Common exam traps
The trap here is that candidates often confuse root guard (which protects against becoming a root port) with preventing the switch from becoming the root bridge, or they mistakenly think setting priority to 0 (lowest) would prevent root election, when in fact it forces the switch to become root.
Detailed technical explanation
STP bridge priority is a 16-bit value that, combined with the switch MAC address, determines the bridge ID. The priority must be configured in multiples of 4096 (the system ID extension is used for VLANs in PVST+). A priority of 61440 (0xF000) is the highest configurable value (excluding the reserved value of 65535), ensuring the new switch will not become root unless all other switches have even higher priorities. In a migration scenario, this allows the new switch to participate in the topology without triggering a root bridge election, maintaining stability.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
What to study next
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Network Fundamentals — study guide chapter
Learn the concepts, then practise the questions
Network Fundamentals practice questions
Targeted practice on this topic area only
All 200-901 questions
505 questions across all exam domains
Cisco DevNet Associate 200-901 study guide
Full concept coverage aligned to exam objectives
200-901 practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Practise 200-901 questions linked to Software Development and Design.
Practise 200-901 questions linked to Understanding and Using APIs.
Practise 200-901 questions linked to Cisco Platforms and Development.
Practise 200-901 questions linked to Application Deployment and Security.
Practise 200-901 questions linked to Infrastructure and Automation.
Practise 200-901 questions linked to Network Fundamentals.
Practise 200-901 questions linked to 200-901 fundamentals.
Practise 200-901 questions linked to 200-901 scenario.
Practise 200-901 questions linked to 200-901 troubleshooting.
Practice this exam
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Network Fundamentals — This question tests Network Fundamentals — Read the scenario before looking for a memorised answer..
The correct answer is: Configure the bridge priority to 61440 — Option B is correct because setting the bridge priority to 61440 (which is a valid priority value in increments of 4096) ensures the new switch has a higher numerical priority than the current root bridge, preventing it from becoming the root. In STP/RSTP, the switch with the lowest bridge priority becomes the root bridge; by configuring a high priority, the new switch will not disrupt the existing topology.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Last reviewed: Jun 11, 2026
This 200-901 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 200-901 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.