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300-410 Practice Question: Which TWO statements about TACACS+ and RADIUS are…
Which TWO statements about TACACS+ and RADIUS are true? (Choose TWO.)
⚠ Common exam trap
Cisco often tests the misconception that RADIUS encrypts the entire payload like TACACS+, or that TACACS+ uses UDP, leading candidates to incorrectly select option B or C.
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, including the username and password, using a shared secret.
A is correct because TACACS+ encrypts the entire packet body, including the username and password, using a shared secret. This provides confidentiality for all authentication and authorization data, unlike RADIUS which only encrypts the password field.
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, including the username and password, using a shared secret.
Why this is correct
TACACS+ encrypts the entire payload (except the header) using the shared secret, providing full confidentiality for authentication data.
- ✗
RADIUS encrypts the entire packet payload, including the username and password, using a shared secret.
Why it's wrong here
RADIUS encrypts only the password field in the Access-Request packet; other fields like username are sent in cleartext.
- ✗
TACACS+ uses UDP port 49 by default for communication.
Why it's wrong here
TACACS+ uses TCP port 49 by default, not UDP; RADIUS uses UDP ports 1812 (authentication) and 1813 (accounting).
- ✓
RADIUS combines authentication and authorization in a single packet, while TACACS+ separates them.
Why this is correct
RADIUS bundles authentication and authorization together in the Access-Accept packet, whereas TACACS+ uses separate packets for each AAA function.
- ✗
Both TACACS+ and RADIUS support per-command authorization for exec sessions.
Why it's wrong here
Only TACACS+ supports per-command authorization; RADIUS does not natively support command-level authorization in Cisco IOS.
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.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 300-410 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 300-410 exam.