Question 780 of 2,015

AAA, RADIUS, and TACACS+ →mediumMultiple ChoiceObjective-mapped

Quick Answer

The answer is that the switch is missing the `aaa accounting dot1x default start-stop group radius` command to enable RADIUS accounting for 802.1X sessions. While the `radius-server host` command correctly defines the server’s IP, authentication port 1812, accounting port 1813, and shared secret, it does not activate accounting for any service—it merely registers the server as a target. The `aaa authentication dot1x default group radius` command only handles authentication; accounting requires a separate global directive specifying the service (dot1x), the record-trigger mode (start-stop), and the server group. On the ENCOR 350-401 exam, this scenario tests your understanding that AAA accounting is not inherited from authentication configuration—a common trap is assuming that defining an accounting port alone enables accounting. Remember the mnemonic: “Auth gets you in, Accounting tracks the sin”—you must explicitly command the switch to send start and stop records.

350-401 AAA, RADIUS, and TACACS+ Practice Question

This 350-401 practice question tests your understanding of aaa, radius, and tacacs+. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 network engineer is configuring a Cisco switch for 802.1X with RADIUS authentication. The switch is also configured with 'aaa authentication dot1x default group radius'. The engineer wants to use a single RADIUS server for both authentication and accounting. The RADIUS server is configured with the same shared secret for both services. The engineer configures 'radius-server host 10.1.1.1 auth-port 1812 acct-port 1813 key cisco123'. However, accounting records are not being sent to the server. The engineer verifies that the RADIUS server is reachable and that accounting is enabled on the server. 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.

Question 1mediummultiple choice

Study the full AAA explanation →

A
The switch is missing the 'aaa accounting dot1x default start-stop group radius' command to enable accounting for 802.1X sessions.
Correct because accounting is a separate AAA function that must be explicitly configured; the RADIUS server definition alone does not enable accounting.
B
The RADIUS server is using a different accounting port than 1813; the switch should use port 1646.
Why wrong: Incorrect because RADIUS accounting officially uses UDP port 1813; port 1646 is legacy but still used by some servers. However, the scenario states the server is configured with the same secret for both, and the port is likely correct; the issue is missing accounting configuration.
C
The switch must have 'aaa new-model' configured before accounting can work.
Why wrong: Incorrect because 'aaa new-model' is already implied by the authentication configuration; it is a prerequisite but not the missing piece.
D
The RADIUS server's shared secret for accounting is different from the authentication secret.
Why wrong: Incorrect because the scenario says the server is configured with the same shared secret for both services, and the switch uses the same key for both ports.

Full breakdown with real-world context →

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 switch is missing the 'aaa accounting dot1x default start-stop group radius' command to enable accounting for 802.1X sessions.

The switch must have accounting enabled globally and for the specific service (dot1x). The 'radius-server host' command only defines the server; accounting is not automatically enabled. The engineer needs to configure 'aaa accounting dot1x default start-stop group radius' to send accounting records.

Key principle: Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.

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 switch is missing the 'aaa accounting dot1x default start-stop group radius' command to enable accounting for 802.1X sessions.
Why this is correct
Correct because accounting is a separate AAA function that must be explicitly configured; the RADIUS server definition alone does not enable accounting.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Authentication checks who the user is.
✗
The RADIUS server is using a different accounting port than 1813; the switch should use port 1646.
Why it's wrong here
Incorrect because RADIUS accounting officially uses UDP port 1813; port 1646 is legacy but still used by some servers. However, the scenario states the server is configured with the same secret for both, and the port is likely correct; the issue is missing accounting configuration.
✗
The switch must have 'aaa new-model' configured before accounting can work.
Why it's wrong here
Incorrect because 'aaa new-model' is already implied by the authentication configuration; it is a prerequisite but not the missing piece.
✗
The RADIUS server's shared secret for accounting is different from the authentication secret.
Why it's wrong here
Incorrect because the scenario says the server is configured with the same shared secret for both services, and the switch uses the same key for both ports.

Common exam traps

Common exam trap: authentication is not authorization

Logging in proves the user can authenticate. It does not automatically mean the user is allowed to enter privileged or configuration mode. Watch for AAA authorization, privilege level and command authorization details.

Trap categories for this question

Scenario analysis trap
Incorrect because RADIUS accounting officially uses UDP port 1813; port 1646 is legacy but still used by some servers. However, the scenario states the server is configured with the same secret for both, and the port is likely correct; the issue is missing accounting configuration.

Detailed technical explanation

How to think about this question

This kind of question is testing the difference between identity and permission. A user may successfully log in to a router because authentication is working, but still fail to enter configuration mode because authorization is missing, misconfigured or mapped to a lower privilege level.

KKey Concepts to Remember

Authentication checks who the user is.
Authorization controls what the user is allowed to do after login.
Privilege levels affect access to EXEC and configuration commands.
AAA, TACACS+ and RADIUS can separate login success from command access.

TExam Day Tips

Do not assume successful login means full administrative access.
Look for words such as cannot enter configuration mode, privilege level, authorization or command access.
Separate login problems from permission problems before choosing the answer.

Key takeaway

Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.

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.

Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related 350-401 questions on access control and AAA configuration.

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FAQ

Questions learners often ask

What does this 350-401 question test?

AAA, RADIUS, and TACACS+ — This question tests AAA, RADIUS, and TACACS+ — Authentication checks who the user is..

What is the correct answer to this question?

The correct answer is: The switch is missing the 'aaa accounting dot1x default start-stop group radius' command to enable accounting for 802.1X sessions. — The switch must have accounting enabled globally and for the specific service (dot1x). The 'radius-server host' command only defines the server; accounting is not automatically enabled. The engineer needs to configure 'aaa accounting dot1x default start-stop group radius' to send accounting records.

What should I do if I get this 350-401 question wrong?

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?

Authentication checks who the user is.

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