- A
TACACS+ encrypts the entire packet body, whereas RADIUS only encrypts the password.
Correct because TACACS+ encrypts the entire payload, while RADIUS only encrypts the password attribute.
- B
RADIUS uses TCP for reliable transport, while TACACS+ uses UDP.
Why wrong: Incorrect because RADIUS uses UDP, and TACACS+ uses TCP.
- C
RADIUS combines authentication and authorization in one packet, whereas TACACS+ separates them.
Correct because RADIUS typically combines AAA functions, while TACACS+ uses separate packets for each.
- D
TACACS+ encrypts only the password in the packet, similar to RADIUS.
Why wrong: Incorrect because TACACS+ encrypts the entire packet body, not just the password.
- E
RADIUS uses UDP as its transport protocol, while TACACS+ uses TCP.
Correct because RADIUS uses UDP (ports 1812/1813) and TACACS+ uses TCP (port 49).
Quick Answer
The correct answer is that RADIUS uses UDP as its transport protocol, while TACACS+ uses TCP. This fundamental difference stems from how each protocol handles encryption and packet delivery: RADIUS encrypts only the password in the access-request packet and relies on UDP’s lightweight, connectionless transport for speed, whereas TACACS+ encrypts the entire packet body and uses TCP’s reliable, connection-oriented delivery to ensure complete message integrity. On the ENCOR 350-401 exam, this distinction tests your understanding of AAA architecture and is often paired with the fact that RADIUS combines authentication and authorization into a single process, while TACACS+ separates them into distinct phases. A common trap is assuming both protocols use the same transport or encryption scope—remember that RADIUS is “password-only” and UDP, while TACACS+ is “full-body” and TCP. For a quick memory tip, think “R-UDP” (RADIUS uses UDP) and “T-TCP” (TACACS+ uses TCP), and that TACACS+ encrypts the “Total” packet.
CCNP 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
TACACS+ encrypts the entire packet body, whereas RADIUS only encrypts the password.
The correct answers contrast the two protocols. Option A is correct because TACACS+ encrypts the entire packet body, while RADIUS only encrypts the password. Option C is correct because RADIUS combines authentication and authorization, while TACACS+ separates them. Option E is correct because RADIUS uses UDP (typically port 1812/1813), while TACACS+ uses TCP (port 49). Option B is wrong because RADIUS uses UDP, not TCP. Option D is wrong because TACACS+ encrypts the entire packet body, not just the password.
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.
- ✓
TACACS+ encrypts the entire packet body, whereas RADIUS only encrypts the password.
- ✗
RADIUS uses TCP for reliable transport, while TACACS+ uses UDP.
- ✓
RADIUS combines authentication and authorization in one packet, whereas TACACS+ separates them.
- ✗
TACACS+ encrypts only the password in the packet, similar to RADIUS.
Why it's wrong here
Incorrect because TACACS+ encrypts the entire packet body, not just the password.
- ✓
RADIUS uses UDP as its transport protocol, while TACACS+ uses TCP.
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: TACACS+ encrypts the entire packet body, whereas RADIUS only encrypts the password. — The correct answers contrast the two protocols. Option A is correct because TACACS+ encrypts the entire packet body, while RADIUS only encrypts the password. Option C is correct because RADIUS combines authentication and authorization, while TACACS+ separates them. Option E is correct because RADIUS uses UDP (typically port 1812/1813), while TACACS+ uses TCP (port 49). Option B is wrong because RADIUS uses UDP, not TCP. Option D is wrong because TACACS+ encrypts the entire packet body, not just the password.
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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
1 more ways this is tested on 350-401
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Which three statements about RADIUS and TACACS+ are true? (Choose three.)
hard- ✓ A.RADIUS combines authentication and authorization in a single packet.
- ✓ B.TACACS+ uses TCP port 49 by default.
- C.RADIUS encrypts the entire packet payload for all attributes.
- ✓ D.TACACS+ provides separate authentication, authorization, and accounting processes.
- E.RADIUS supports per-command authorization for shell sessions.
Why A: 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.
Last reviewed: Jun 18, 2026
This 350-401 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 350-401 exam.
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