The answer is EAP-TLS, because it requires a client certificate that the Windows 10 clients lack, while PEAP-MSCHAPv2 relies on username and password authentication inside a TLS tunnel. When the Cisco ISE is configured to require EAP-TLS, any client attempting PEAP-MSCHAPv2 will fail at the EAP negotiation stage, producing an “EAP failure” log entry. On the ENCOR 350-401 exam, this scenario tests your understanding of how 802.1X authentication methods differ in credential requirements—a common trap is assuming all tunneled methods are interchangeable. Remember that EAP-TLS is certificate-based on both sides, whereas PEAP-MSCHAPv2 only needs a server certificate. A useful memory tip: “TLS needs a TLS (certificate) on both ends; PEAP only protects the password.”
350-401 Infrastructure Security Practice Question
This 350-401 practice question tests your understanding of infrastructure security. 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.
An enterprise network uses 802.1X for wired access. The authentication server is a Cisco ISE. Recently, some Windows 10 clients fail to authenticate, while others succeed. The engineer checks the switch configuration and finds 'authentication port-control auto' and 'dot1x pae authenticator' are configured. The failing clients show 'EAP failure' in the logs. The engineer suspects a mismatch in EAP method. Which EAP method is most likely causing the issue if the ISE is configured to require EAP-TLS but the Windows clients are configured for PEAP-MSCHAPv2?
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
✓
EAP-TLS requires a client certificate, which the Windows clients do not have.
EAP-TLS requires a client certificate, while PEAP-MSCHAPv2 uses a username/password inside a TLS tunnel. If ISE is configured to only accept EAP-TLS, clients attempting PEAP will receive an EAP failure. Option A is correct because EAP-TLS is certificate-based and different from PEAP. Option B is incorrect because EAP-FAST uses a PAC, not certificates. Option C is incorrect because LEAP is deprecated and uses MS-CHAPv2, but it is not the same as PEAP. Option D is incorrect because EAP-MD5 is a simple challenge-response and not typically used in enterprise 802.1X.
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.
✓
EAP-TLS requires a client certificate, which the Windows clients do not have.
Why this is correct
Correct because EAP-TLS requires client certificates, and PEAP-MSCHAPv2 does not provide them.
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.
✗
EAP-FAST requires a PAC file that the Windows clients do not have.
Why it's wrong here
Incorrect because the scenario describes a mismatch between EAP-TLS and PEAP, not EAP-FAST.
✗
LEAP uses a shared secret that is not configured on the clients.
Why it's wrong here
Incorrect because LEAP is not mentioned and is not the method in question.
✗
EAP-MD5 does not support mutual authentication, causing the failure.
Why it's wrong here
Incorrect because EAP-MD5 is not the method used by the clients or server.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Trap categories for this question
Scenario analysis trap
Incorrect because the scenario describes a mismatch between EAP-TLS and PEAP, not EAP-FAST.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 practitioner preparing for the 350-401 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 350-401 question in full detail.
Identify which 350-401 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Infrastructure Security — This question tests Infrastructure Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: EAP-TLS requires a client certificate, which the Windows clients do not have. — EAP-TLS requires a client certificate, while PEAP-MSCHAPv2 uses a username/password inside a TLS tunnel. If ISE is configured to only accept EAP-TLS, clients attempting PEAP will receive an EAP failure. Option A is correct because EAP-TLS is certificate-based and different from PEAP. Option B is incorrect because EAP-FAST uses a PAC, not certificates. Option C is incorrect because LEAP is deprecated and uses MS-CHAPv2, but it is not the same as PEAP. Option D is incorrect because EAP-MD5 is a simple challenge-response and not typically used in enterprise 802.1X.
What should I do if I get this 350-401 question wrong?
Identify which 350-401 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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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