This 200-901 practice question tests your understanding of network fundamentals. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
A network engineer notices that after a link failure, traffic to a server on a different VLAN is intermittent. The network uses Rapid PVST+. The switch connecting the server is a root bridge for that VLAN. What is the most likely cause of the intermittent connectivity?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The server port is not configured as an edge port, causing STP convergence delay.
When a link fails in a Rapid PVST+ network, the switch that is the root bridge for the VLAN must reconverge. If the server port is not configured as an edge port (using the 'spanning-tree portfast' command), the switch will transition the port through the listening and learning states (even with Rapid PVST+, non-edge ports still undergo a brief convergence delay). This delay causes intermittent connectivity until the port reaches the forwarding state.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
The server port is not configured as an edge port, causing STP convergence delay.
Why this is correct
Non-edge ports go through STP states, causing delays.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The server is sending BPDUs with a higher priority.
Why it's wrong here
Servers typically don't send BPDUs.
✗
The root bridge is flapping due to a configuration mismatch.
Why it's wrong here
Root bridge flapping is not typical for rapid PVST+.
✗
OSPF hold-down timers are preventing route updates.
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that Rapid PVST+ eliminates all convergence delays, but the trap here is that non-edge ports still require a brief transition delay, and candidates may forget that PortFast (edge port configuration) is necessary to avoid this delay for host-facing ports.
Detailed technical explanation
How to think about this question
In Rapid PVST+, edge ports (PortFast) immediately transition to forwarding state, bypassing the listening/learning states. Without this configuration, even with RSTP's rapid transition mechanism, a port that is not edge will still undergo a short delay (typically 3-4 seconds) to ensure no loops exist. In a real-world scenario, if a server is connected to a root bridge and a link fails, the root bridge must reconverge its ports; if the server port is not edge, the delay can cause timeouts for applications sensitive to brief outages.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Network Fundamentals — This question tests Network Fundamentals — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The server port is not configured as an edge port, causing STP convergence delay. — When a link fails in a Rapid PVST+ network, the switch that is the root bridge for the VLAN must reconverge. If the server port is not configured as an edge port (using the 'spanning-tree portfast' command), the switch will transition the port through the listening and learning states (even with Rapid PVST+, non-edge ports still undergo a brief convergence delay). This delay causes intermittent connectivity until the port reaches the forwarding state.
What should I do if I get this 200-901 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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