Question 96 of 750

Wireless Security Protocols →hardMultiple ChoiceObjective-mapped

Troubleshooting EAP-TLS Certificate Validation Failures in WPA2-Enterprise

This 220-1202 practice question tests your understanding of wireless security protocols. 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 technician is troubleshooting a wireless network where users report intermittent connectivity and slow speeds. The network uses WPA2-Enterprise with EAP-TLS and certificate-based authentication. The technician notices that the RADIUS server logs show frequent certificate validation failures. What is the most likely root 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.

A
The access point's firmware is outdated, causing packet loss.
Why wrong: Incorrect. Firmware issues would affect all traffic, not specifically certificate validation.
B
The RADIUS server's certificate has expired.
Why wrong: Incorrect. If the server certificate were expired, all clients would fail authentication, not just some.
C
Client devices have expired or untrusted certificates.
Correct. Expired client certificates cause intermittent authentication failures, leading to disconnects and reconnects.
D
The wireless channel is overlapping with neighboring networks.
Why wrong: Incorrect. Channel overlap causes slow speeds and interference, not certificate validation errors.

Full breakdown with real-world context →

Quick Answer

The answer is client devices have expired or untrusted certificates. EAP-TLS in WPA2-Enterprise requires mutual certificate-based authentication, meaning both the RADIUS server and the client must present valid, trusted certificates. When client certificates expire or are not trusted by the server, the handshake fails, causing the intermittent connectivity and slow speeds as clients repeatedly attempt reauthentication. On the CompTIA A+ Core 2 220-1202 exam, this scenario tests your understanding of certificate lifecycle management in enterprise wireless security; a common trap is assuming the issue lies with the server certificate or a simple password mismatch, since EAP-TLS uses certificates, not shared secrets. Remember the key distinction: EAP-TLS is certificate-driven on both ends, so expired client certs break the chain. Memory tip: "TLS = Two-sided trust; if either side's cert is toast, the connection is lost."

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

✓

Client devices have expired or untrusted certificates.

The RADIUS server logs show frequent certificate validation failures, which directly points to an issue with the certificates presented by the clients during EAP-TLS authentication. In WPA2-Enterprise with EAP-TLS, both the server and client must present valid certificates; if client certificates are expired or untrusted, the RADIUS server will reject the authentication, causing intermittent connectivity and slow speeds as clients fail to re-authenticate or roam.

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 access point's firmware is outdated, causing packet loss.
Why it's wrong here
Incorrect. Firmware issues would affect all traffic, not specifically certificate validation.
✗
The RADIUS server's certificate has expired.
Why it's wrong here
Incorrect. If the server certificate were expired, all clients would fail authentication, not just some.
✓
Client devices have expired or untrusted certificates.
Why this is correct
Correct. Expired client certificates cause intermittent authentication failures, leading to disconnects and reconnects.
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 wireless channel is overlapping with neighboring networks.
Why it's wrong here
Incorrect. Channel overlap causes slow speeds and interference, not certificate validation errors.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Cisco often tests the distinction between server-side and client-side certificate issues; the trap here is that candidates may assume the RADIUS server's certificate is the problem (Option B) because it is the central authentication point, but the logs specifically show 'validation failures' which in EAP-TLS typically refer to the client certificate failing validation by the server.

Detailed technical explanation

How to think about this question

EAP-TLS requires mutual certificate authentication: the RADIUS server validates the client certificate against a trusted CA, and the client validates the server certificate. If a client certificate is expired or issued by an untrusted CA, the RADIUS server will log an authentication failure with a reason code like 'certificate validation failed' (RFC 5216). In real-world deployments, this often happens when client certificates are not renewed before expiry or when a new CA is deployed without updating trust stores on clients.

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.

Quick reference

AAA Protocol Comparison

Protocol	Port(s)	Encryption	Transport	Primary Use
RADIUS	1812 / 1813	Password only	UDP	Network access control
TACACS+	49	Full packet	TCP	Device administration
Diameter	3868	Full session	TCP / SCTP	Carrier / mobile networks
802.1X	—	EAP-based	Layer 2	Port-based access control

TACACS+ encrypts the entire packet; RADIUS only encrypts the password field — a key exam distinction.

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.

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FAQ

Questions learners often ask

What does this 220-1202 question test?

Wireless Security Protocols — This question tests Wireless Security Protocols — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: Client devices have expired or untrusted certificates. — The RADIUS server logs show frequent certificate validation failures, which directly points to an issue with the certificates presented by the clients during EAP-TLS authentication. In WPA2-Enterprise with EAP-TLS, both the server and client must present valid certificates; if client certificates are expired or untrusted, the RADIUS server will reject the authentication, causing intermittent connectivity and slow speeds as clients fail to re-authenticate or roam.

What should I do if I get this 220-1202 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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