- A
RADIUS combines authentication and authorization in a single packet.
Correct because RADIUS merges authentication and authorization in the Access-Accept packet.
- B
TACACS+ uses TCP port 49 by default.
Correct because TACACS+ uses TCP port 49 for reliable delivery.
- C
RADIUS encrypts the entire packet payload for all attributes.
Why wrong: Incorrect because RADIUS only encrypts the password field; other attributes are sent in cleartext.
- D
TACACS+ provides separate authentication, authorization, and accounting processes.
Correct because TACACS+ uses distinct packets for each AAA function, allowing granular control.
- E
RADIUS supports per-command authorization for shell sessions.
Why wrong: Incorrect because per-command authorization is a feature of TACACS+, not RADIUS.
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 three statements about RADIUS and TACACS+ are true? (Choose three.)
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 combines authentication and authorization in a single packet.
RADIUS and TACACS+ are both AAA protocols but differ in transport, encryption, and authorization granularity. RADIUS uses UDP and encrypts only the password; TACACS+ uses TCP and encrypts the entire packet. TACACS+ supports per-command authorization, while RADIUS does not. Both can be used for device administration, but RADIUS is more common for network access.
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 combines authentication and authorization in a single packet.
Why this is correct
Correct because RADIUS merges authentication and authorization in the Access-Accept packet.
Related concept
Authentication checks who the user is.
- ✓
TACACS+ uses TCP port 49 by default.
- ✗
RADIUS encrypts the entire packet payload for all attributes.
Why it's wrong here
Incorrect because RADIUS only encrypts the password field; other attributes are sent in cleartext.
- ✓
TACACS+ provides separate authentication, authorization, and accounting processes.
- ✗
RADIUS supports per-command authorization for shell sessions.
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
Command / output trap
Incorrect because per-command authorization is a feature of TACACS+, not RADIUS.
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 combines authentication and authorization in a single packet. — RADIUS and TACACS+ are both AAA protocols but differ in transport, encryption, and authorization granularity. RADIUS uses UDP and encrypts only the password; TACACS+ uses TCP and encrypts the entire packet. TACACS+ supports per-command authorization, while RADIUS does not. Both can be used for device administration, but RADIUS is more common for network access.
What should I do if I get this 350-401 question wrong?
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.
What is the key concept behind this question?
Authentication checks who the user is.
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Last reviewed: Jun 18, 2026
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