The answer is that the health probe path is set to an incorrect endpoint on the origin servers. Azure Front Door relies on health probes to verify origin availability, sending HTTP GET requests to a specific path; if that path does not return a 200 OK status—for instance, pointing to a missing resource or a page that redirects—Front Door incorrectly marks the origin as unhealthy, or fails to detect the failure, which directly blocks failover. On the Microsoft Cybersecurity Architect exam, this scenario tests your understanding of how Front Door’s health monitoring logic interacts with origin configuration, often appearing as a trap where candidates blame network issues or routing rules instead of the probe path. A common memory tip is “Probe path, not ping”—remember that Front Door checks a URL, not a server’s IP reachability, so always verify the exact endpoint returns a 200.
SC-100 Design security for infrastructure Practice Question
This SC-100 practice question tests your understanding of design security for infrastructure. 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 company uses Azure Front Door to load balance traffic across two origin servers in different Azure regions. They notice that failover is not working when one origin becomes unhealthy. What is the most likely cause?
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 health probe path is set to an incorrect endpoint on the origin servers.
The most likely cause is that the health probe path is set to an incorrect endpoint on the origin servers. Azure Front Door uses health probes to determine the health of each origin; if the probe path does not return a 200 OK status (e.g., it points to a missing page or a resource that doesn't exist), Front Door will mark that origin as unhealthy and stop routing traffic to it. Since failover is not occurring, the healthy origin is not being detected as healthy, or the unhealthy origin is not being detected as unhealthy, which directly prevents proper failover.
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.
✗
Both origins are in the same region.
Why it's wrong here
The scenario states they are in different regions, so this is not the issue.
✗
Caching is enabled on the Front Door profile.
Why it's wrong here
Caching affects content delivery, not failover.
✗
Session affinity is enabled.
Why it's wrong here
Session affinity ensures traffic is directed to the same origin; it does not prevent failover.
✓
The health probe path is set to an incorrect endpoint on the origin servers.
Why this is correct
An incorrect health probe path can cause Front Door to consider the origin healthy when it is not, or vice versa.
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume failover issues are caused by regional or caching settings, but the real culprit is almost always a misconfigured health probe path that prevents Front Door from accurately assessing origin health.
Trap categories for this question
Scenario analysis trap
The scenario states they are in different regions, so this is not the issue.
Detailed technical explanation
How to think about this question
Azure Front Door sends HTTP/HTTPS health probes to the configured path (default is '/') on each origin every 30 seconds (configurable). If the origin returns a non-200 status (e.g., 404, 500) or fails to respond within the timeout, Front Door marks it as unhealthy and removes it from the load-balancing rotation. A common misconfiguration is setting the health probe path to a static file that exists on one origin but not the other, or to a dynamic endpoint that requires authentication, causing the probe to fail and the origin to be incorrectly marked as unhealthy.
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 cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this SC-100 question in full detail.
Design security for infrastructure — This question tests Design security for infrastructure — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The health probe path is set to an incorrect endpoint on the origin servers. — The most likely cause is that the health probe path is set to an incorrect endpoint on the origin servers. Azure Front Door uses health probes to determine the health of each origin; if the probe path does not return a 200 OK status (e.g., it points to a missing page or a resource that doesn't exist), Front Door will mark that origin as unhealthy and stop routing traffic to it. Since failover is not occurring, the healthy origin is not being detected as healthy, or the unhealthy origin is not being detected as unhealthy, which directly prevents proper failover.
What should I do if I get this SC-100 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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