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350-401 Practice Question: Which three statements about RADIUS and TACACS+…
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.
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.
- ✓
TACACS+ uses TCP port 49 by default.
Why this is correct
Correct because TACACS+ uses TCP port 49 for reliable delivery.
- ✗
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.
Why this is correct
Correct because TACACS+ uses distinct packets for each AAA function, allowing granular control.
- ✗
RADIUS supports per-command authorization for shell sessions.
Why it's wrong here
Incorrect because per-command authorization is a feature of TACACS+, not RADIUS.
Quick reference
AAA Protocol Comparison
| Protocol | Port(s) | Encryption | Transport | Primary Use |
|---|---|---|---|---|
| RADIUS | 1812 / 1813 | Password only | UDP | Network access control |
| TACACS+ | 49 | Full packet | TCP | Device administration |
| Diameter | 3868 | Full session | TCP / SCTP | Carrier / mobile networks |
| 802.1X | — | EAP-based | Layer 2 | Port-based access control |
TACACS+ encrypts the entire packet; RADIUS only encrypts the password field — a key exam distinction.
Go deeper
Related to this question
Learn chapter
Network Architecture Fundamentals
Key term
802.1X Authentication
802.1X is a network access control protocol that prevents unauthorized devices from connecting to a wired or wireless network by requiring them to authenticate before gaining access.
Key term
RADIUS vs TACACS+
RADIUS and TACACS+ are two network protocols used to verify user identities and control access to network devices and services, with different approaches to security and flexibility.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.