350-501 Security and Services Practice Question
An SP engineer is hardening management plane access on IOS XR routers. They want to enforce role-based access control using task groups. Which AAA protocol is required to support attribute-based authorization on IOS XR?
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+
TACACS+ supports per-command authorization and attribute-value pairs for role-based access, while RADIUS has limited authorization capabilities. IOS XR uses TACACS+ for task group-based authorization.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Kerberos
Why it's wrong here
Kerberos is not commonly used for device administration AAA.
- ✓
TACACS+
Why this is correct
TACACS+ provides granular command authorization and is used with IOS XR task groups.
- ✗
RADIUS
Why it's wrong here
RADIUS does not support per-command authorization as needed for task groups.
- ✗
LDAP
Why it's wrong here
LDAP is not typically used for AAA in Cisco IOS XR; it's for directory services.
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 350-501 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 350-501 exam.