The answer is to run the 'test aaa authentication login <user> <password> legacy' command. This command is the correct first step when troubleshooting TACACS+ authentication on a Nexus switch because it directly simulates the exact authentication flow the switch uses against the TACACS+ server, bypassing the need for a full login session. By using the 'legacy' keyword, the test isolates whether the failure stems from the AAA configuration itself—such as incorrect shared secrets or server group definitions—rather than from network connectivity or server reachability issues. On the Cisco DCCOR 350-601 exam, this scenario tests your ability to differentiate between diagnostic commands; a common trap is to immediately check network connectivity or server logs, which wastes time if the AAA configuration is misconfigured. Remember the memory tip: "Test before you guess—legacy tests the AAA mess."
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 is configuring AAA on a Cisco Nexus switch to authenticate management access via TACACS+. The switch is reachable, but login attempts repeatedly fail. Which action should the engineer take to isolate the issue?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Run 'test aaa authentication login <user> <password> legacy' to validate AAA configuration.
Option B is correct because the 'test aaa authentication login' command with the 'legacy' keyword directly validates the AAA authentication configuration against the TACACS+ server without requiring a full login session. This isolates whether the issue is with the AAA configuration itself versus network connectivity or server reachability, as the command simulates the exact authentication flow the switch uses.
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.
✗
Enable 'debug tacacs' on the switch to see detailed TACACS+ exchange.
Why it's wrong here
Debug should be used after other isolation steps due to impact.
✓
Run 'test aaa authentication login <user> <password> legacy' to validate AAA configuration.
Why this is correct
This command directly tests the AAA authentication process.
Related concept
Read the scenario before looking for a memorised answer.
✗
Verify IP connectivity to the TACACS+ server using ping.
Why it's wrong here
Ping only tests network reachability, not AAA authentication.
✗
Check if the TACACS+ server port (49) is open using Telnet.
Why it's wrong here
Telnet to port 49 may not be allowed; better to test AAA directly.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between connectivity verification (ping, port checks) and actual AAA authentication validation, trapping candidates who assume that reachability implies correct AAA operation, when in fact the shared secret, server configuration, or authentication method may be misconfigured.
Detailed technical explanation
How to think about this question
The 'test aaa authentication login' command with the 'legacy' keyword sends a TACACS+ authentication request using the configured server and shared secret, and returns a success or failure message that includes the reason (e.g., invalid password, server unreachable, authentication denied). This command bypasses any local fallback methods, so it directly tests the TACACS+ path, which is critical because TACACS+ encrypts the entire authentication payload (not just the password) and uses TCP port 49, making simple connectivity tests insufficient to diagnose shared secret mismatches or server-side configuration errors.
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: Run 'test aaa authentication login <user> <password> legacy' to validate AAA configuration. — Option B is correct because the 'test aaa authentication login' command with the 'legacy' keyword directly validates the AAA authentication configuration against the TACACS+ server without requiring a full login session. This isolates whether the issue is with the AAA configuration itself versus network connectivity or server reachability, as the command simulates the exact authentication flow the switch uses.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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