Question 845 of 2,015

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

Quick Answer

The correct answer is that the wait-start accounting method delays service until the accounting start packet is acknowledged by the server. This is because wait-start ensures that the network device does not begin granting access or forwarding traffic until it receives a confirmation from the AAA server that the accounting record has been received, making it the most reliable but also the most latency-sensitive method. On the ENCOR 350-401 exam, this concept tests your understanding of how AAA accounting transport methods like RADIUS (UDP 1646/1813) and TACACS+ (TCP 49) handle session tracking, with wait-start often appearing as a distractor against the more common start-stop method. A common trap is confusing wait-start with start-stop, but remember: wait-start holds the door until the server says "got it," while start-stop just logs the entry and exit. Memory tip: think "Wait for the Acknowledgment" to recall that wait-start pauses service until the server confirms the start packet.

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

This 350-401 practice question tests your understanding of aaa, radius, and tacacs+. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 two statements about AAA accounting are true? (Choose two.)

Question 1mediummulti select

Study the full AAA explanation →

A
RADIUS accounting uses UDP as the transport protocol.
Correct because RADIUS uses UDP for both authentication and accounting.
B
TACACS+ accounting uses UDP as the transport protocol.
Why wrong: Incorrect because TACACS+ uses TCP, not UDP.
C
The wait-start accounting method delays service until the accounting start packet is acknowledged by the server.
Correct because wait-start holds the connection until the AAA server confirms receipt of the start record.
D
AAA accounting is only supported for EXEC sessions, not for network access.
Why wrong: Incorrect because accounting can be configured for EXEC, network, connection, and system events.
E
TACACS+ encrypts only the password portion of the accounting packet.
Why wrong: Incorrect because TACACS+ encrypts the entire packet body, not just the password.

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

✓

RADIUS accounting uses UDP as the transport protocol.

AAA accounting tracks user activities and resource usage. RADIUS accounting uses UDP ports 1646/1813, while TACACS+ uses TCP port 49. Accounting can be start-stop, stop-only, or wait-start. The wait-start method delays service until the accounting start is acknowledged, which can impact user experience. TACACS+ encrypts the entire packet, including accounting data.

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.

✓
RADIUS accounting uses UDP as the transport protocol.
Why this is correct
Correct because RADIUS uses UDP for both authentication and accounting.
Related concept
Authentication checks who the user is.
✗
TACACS+ accounting uses UDP as the transport protocol.
Why it's wrong here
Incorrect because TACACS+ uses TCP, not UDP.
✓
The wait-start accounting method delays service until the accounting start packet is acknowledged by the server.
Why this is correct
Correct because wait-start holds the connection until the AAA server confirms receipt of the start record.
Related concept
Authentication checks who the user is.
✗
AAA accounting is only supported for EXEC sessions, not for network access.
Why it's wrong here
Incorrect because accounting can be configured for EXEC, network, connection, and system events.
✗
TACACS+ encrypts only the password portion of the accounting packet.
Why it's wrong here
Incorrect because TACACS+ encrypts the entire packet body, not just the password.

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.

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: RADIUS accounting uses UDP as the transport protocol. — AAA accounting tracks user activities and resource usage. RADIUS accounting uses UDP ports 1646/1813, while TACACS+ uses TCP port 49. Accounting can be start-stop, stop-only, or wait-start. The wait-start method delays service until the accounting start is acknowledged, which can impact user experience. TACACS+ encrypts the entire packet, including accounting data.

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

What is the key concept behind this question?

Authentication checks who the user is.

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