The answer is that the device has not been configured with any RADIUS server host. This is correct because when RADIUS authentication fails and the server logs show no incoming requests, it indicates the network device is not sending any traffic to the RADIUS server at all. Without a configured server host—meaning no IP address or hostname is specified under the RADIUS configuration—the device has no destination to which it can forward authentication packets, so it never initiates communication. On the Cisco DCCOR 350-601 exam, this scenario tests your understanding of the AAA configuration hierarchy: you must first define the server host before applying it to an authentication method list. A common trap is to assume the issue lies with shared secrets or server reachability, but the absence of any server logs points squarely to a missing host definition. Memory tip: “No host, no request”—if the server sees zero packets, check the device’s RADIUS server host list first.
350-601 Security Practice Question
This 350-601 practice question tests your understanding of 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 engineer notices that AAA authentication using RADIUS is failing, and the RADIUS server logs show no incoming authentication requests. Which of the following 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 device has not been configured with any RADIUS server host
If the RADIUS server logs show no incoming authentication requests, the issue is that the device is not sending any traffic to the server. This occurs when no RADIUS server host is configured on the device, meaning the device has no IP address or hostname to which it can send authentication packets. Without a configured server host, the device will not attempt any RADIUS communication, resulting in zero requests reaching the server.
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 device has not been configured with any RADIUS server host
Why this is correct
Without a configured server host, no RADIUS requests are generated, so no logs appear.
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 device is using TACACS+ instead of RADIUS
Why it's wrong here
If TACACS+ is used, no RADIUS requests are sent, but the engineer would know the protocol in use.
✗
The RADIUS server is not reachable due to a firewall
Why it's wrong here
If the server is unreachable, the device would still attempt to send requests (which might be logged depending on firewall).
✗
The RADIUS shared secret is incorrect
Why it's wrong here
An incorrect shared secret would cause authentication failure, but the server would still receive and log the request.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between configuration errors that prevent packet generation (like missing server host) versus errors that cause packet rejection or timeout (like wrong secret or firewall), and the trap here is assuming that any authentication failure must involve network-level issues rather than a missing fundamental configuration element.
Detailed technical explanation
How to think about this question
Under the hood, the RADIUS client (the network device) uses the configured server IP address and UDP port 1812 (or 1645 legacy) to send Access-Request packets. If no server host is defined via the 'radius-server host' command, the device has no destination for RADIUS traffic, so no packets are generated. In real-world scenarios, this often happens after a fresh configuration or when a server is removed but the AAA method list still references RADIUS, causing authentication to silently fail without any network activity.
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.
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.
Security — This question tests Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The device has not been configured with any RADIUS server host — If the RADIUS server logs show no incoming authentication requests, the issue is that the device is not sending any traffic to the server. This occurs when no RADIUS server host is configured on the device, meaning the device has no IP address or hostname to which it can send authentication packets. Without a configured server host, the device will not attempt any RADIUS communication, resulting in zero requests reaching the server.
What should I do if I get this 350-601 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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