The answer is debug tacacs, show tacacs, and test aaa group tacacs+ <username> <password>. These three commands are essential for TACACS+ authentication troubleshooting because they cover the full diagnostic cycle: debug tacacs provides real-time, packet-level visibility into authentication, authorization, and accounting exchanges, allowing you to spot exactly where a failure occurs; show tacacs offers a statistical snapshot of server status, success and failure counts, and pending requests to verify connectivity and performance; and test aaa group tacacs+ <username> <password> directly simulates an authentication attempt against the configured server group, confirming reachability and credential validity without requiring a live user login. On the Cisco CCNP ENARSI 300-410 exam, this question tests your ability to isolate AAA issues in a multi-server environment, and a common trap is confusing show tacacs with show aaa servers—the former is specific to TACACS+ statistics. A useful memory tip is to think of the three D’s: Debug the traffic, Display the stats, and Directly test the credentials.
300-410 Device Access Control Practice Question
This 300-410 practice question tests your understanding of device access control. 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.
Which THREE commands are used to troubleshoot and verify device access control when using TACACS+ authentication on a Cisco IOS router? (Choose THREE.)
This command provides detailed debugging of TACACS+ authentication and authorization packets.
B
show tacacs
This command shows TACACS+ server connection status, statistics, and failures.
C
test aaa group tacacs+ <username> <password>
This command tests authentication against a TACACS+ server group, verifying connectivity and credentials.
D
debug radius authentication
Why wrong: This is for RADIUS, not TACACS+; it would not help with TACACS+ issues.
E
show aaa method-list
Why wrong: This command shows all configured method lists, but it is not specific to TACACS+ and does not provide real-time troubleshooting like the others.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
debug tacacs
Option A is correct because the 'debug tacacs' command enables real-time logging of TACACS+ authentication, authorization, and accounting transactions, allowing you to observe the exact packets exchanged between the router and the TACACS+ server, including authentication failures or successes. Option B is correct because 'show tacacs' displays the current TACACS+ server statistics, including the number of successful and failed authentication attempts, server status, and the number of pending requests, which is essential for verifying connectivity and performance. Option C is correct because 'test aaa group tacacs+ <username> <password>' directly tests the TACACS+ authentication process by sending a simulated authentication request to the configured TACACS+ server group, confirming whether the server is reachable and the credentials are valid.
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.
✓
debug tacacs
Why this is correct
This command provides detailed debugging of TACACS+ authentication and authorization packets.
Related concept
Read the scenario before looking for a memorised answer.
✓
show tacacs
Why this is correct
This command shows TACACS+ server connection status, statistics, and failures.
Related concept
Read the scenario before looking for a memorised answer.
✓
test aaa group tacacs+ <username> <password>
Why this is correct
This command tests authentication against a TACACS+ server group, verifying connectivity and credentials.
Related concept
Read the scenario before looking for a memorised answer.
✗
debug radius authentication
Why it's wrong here
This is for RADIUS, not TACACS+; it would not help with TACACS+ issues.
✗
show aaa method-list
Why it's wrong here
This command shows all configured method lists, but it is not specific to TACACS+ and does not provide real-time troubleshooting like the others.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between TACACS+ and RADIUS troubleshooting commands, so the trap here is that candidates may confuse 'debug radius authentication' (Option D) as applicable to TACACS+ or assume that 'show aaa method-list' (Option E) is a valid command for verifying TACACS+ server status, when in fact it does not exist and the correct command is 'show aaa method-lists'.
Trap categories for this question
Command / output trap
This command shows all configured method lists, but it is not specific to TACACS+ and does not provide real-time troubleshooting like the others.
Detailed technical explanation
How to think about this question
TACACS+ encrypts the entire packet body (including the username and password) using a shared secret key, unlike RADIUS which only encrypts the password; this makes 'debug tacacs' particularly useful for inspecting encrypted payloads to verify proper key matching. In real-world scenarios, when TACACS+ authentication fails, 'debug tacacs' might show 'Authentication failure' or 'Server not responding' messages, while 'show tacacs' can reveal if the server is marked as 'dead' due to repeated timeouts, and 'test aaa group tacacs+' can isolate whether the issue is with the server reachability or the credentials themselves.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 300-410 question in full detail.
Device Access Control — This question tests Device Access Control — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: debug tacacs — Option A is correct because the 'debug tacacs' command enables real-time logging of TACACS+ authentication, authorization, and accounting transactions, allowing you to observe the exact packets exchanged between the router and the TACACS+ server, including authentication failures or successes. Option B is correct because 'show tacacs' displays the current TACACS+ server statistics, including the number of successful and failed authentication attempts, server status, and the number of pending requests, which is essential for verifying connectivity and performance. Option C is correct because 'test aaa group tacacs+ <username> <password>' directly tests the TACACS+ authentication process by sending a simulated authentication request to the configured TACACS+ server group, confirming whether the server is reachable and the credentials are valid.
What should I do if I get this 300-410 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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