Question 703 of 750

Wireless Security Protocols →hardMultiple ChoiceObjective-mapped

Troubleshooting RADIUS Authentication Failures on Access Points

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. The network uses WPA2-Enterprise with a RADIUS server. The technician notices that the RADIUS server logs show frequent authentication failures from one specific access point. 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.

A
The access point is using a different channel than the others.
Why wrong: Channel differences affect signal interference, not RADIUS authentication.
B
The RADIUS server certificate has expired.
Why wrong: An expired certificate would cause client authentication failures, not access point-to-RADIUS failures.
C
The access point's RADIUS shared secret is incorrect.
The shared secret is used for authentication between the AP and RADIUS server; a mismatch causes failures.
D
The clients are using WPA2-PSK instead of WPA2-Enterprise.
Why wrong: Client misconfiguration would not cause RADIUS server logs to show failures from the access point.

Full breakdown with real-world context →

Quick Answer

The answer is a mismatched RADIUS shared secret between the access point and the RADIUS server. This is the most likely cause because WPA2-Enterprise relies on the access point acting as a proxy for authentication; the access point and RADIUS server must share a pre-configured secret key to encrypt and validate their communication. When this secret is incorrect on one side, the server rejects the authentication request, logging a failure even though the client credentials may be valid. On the CompTIA A+ Core 2 220-1202 exam, this question tests your ability to distinguish between network-layer issues and authentication-layer misconfigurations—a common trap is blaming channel interference or encryption mismatches, but those would cause connectivity drops or association failures, not specific RADIUS log entries. Remember the memory tip: “Secret mismatch, server dismiss.” If the RADIUS logs show authentication failures from a single access point, always verify the shared secret before touching wireless settings.

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

✓

The access point's RADIUS shared secret is incorrect.

The RADIUS shared secret is a pre-shared key configured on both the access point and the RADIUS server to authenticate the AP itself. If the secret on the specific AP does not match the server's configuration, the server will reject authentication requests from that AP, causing intermittent connectivity for clients associated with it. The logs showing frequent authentication failures from one AP point directly to a mismatch in this shared secret.

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 is using a different channel than the others.
Why it's wrong here
Channel differences affect signal interference, not RADIUS authentication.
✗
The RADIUS server certificate has expired.
Why it's wrong here
An expired certificate would cause client authentication failures, not access point-to-RADIUS failures.
✓
The access point's RADIUS shared secret is incorrect.
Why this is correct
The shared secret is used for authentication between the AP and RADIUS server; a mismatch causes failures.
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 clients are using WPA2-PSK instead of WPA2-Enterprise.
Why it's wrong here
Client misconfiguration would not cause RADIUS server logs to show failures from the access point.

Common exam traps

Common exam trap: answer the scenario, not the keyword

CompTIA often tests the distinction between client-side authentication failures (e.g., wrong PSK or certificate) and infrastructure-side authentication failures (e.g., RADIUS shared secret mismatch), and the trap here is that candidates may confuse a RADIUS server certificate issue with a per-AP shared secret problem, not realizing that a certificate expiry would affect all APs uniformly.

Trap categories for this question

Command / output trap
Client misconfiguration would not cause RADIUS server logs to show failures from the access point.

Detailed technical explanation

How to think about this question

The RADIUS shared secret is used to encrypt and authenticate RADIUS packets (e.g., Access-Request, Access-Accept) between the NAS (the AP) and the RADIUS server, as defined in RFC 2865. A mismatch causes the server to silently drop the request or respond with an Access-Reject, often logged as 'Invalid authenticator' or 'Shared secret mismatch'. In real-world troubleshooting, verifying the shared secret on both ends with a packet capture (looking for RADIUS Access-Request with an invalid authenticator) is a common step.

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 junior network technician can log in to a core router but cannot reach the enable prompt or configuration mode. The AAA server is authenticating the login — but the authorisation policy only grants privilege level 1, not 15. Authentication (who you are) is working; authorisation (what you can do) is not.

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: The access point's RADIUS shared secret is incorrect. — The RADIUS shared secret is a pre-shared key configured on both the access point and the RADIUS server to authenticate the AP itself. If the secret on the specific AP does not match the server's configuration, the server will reject authentication requests from that AP, causing intermittent connectivity for clients associated with it. The logs showing frequent authentication failures from one AP point directly to a mismatch in this shared secret.

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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