350-501 Security and Services Practice Question
A service provider is deploying a BNG for subscriber management. Which protocol is typically used to authenticate subscribers and assign IP addresses in a PPPoE-based broadband network?
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
RADIUS is the standard protocol for authentication, authorization, and accounting (AAA) in BNG environments. DHCP assigns IP addresses, but authentication is via RADIUS. TACACS+ is for device administration; IPoE uses DHCP but not typically for authentication.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
DHCP
Why it's wrong here
DHCP assigns IP addresses but does not authenticate subscribers.
- ✓
RADIUS
Why this is correct
RADIUS is widely used for subscriber AAA in BNG.
- ✗
IPoE
Why it's wrong here
IPoE is an encapsulation method, not an authentication protocol.
- ✗
TACACS+
Why it's wrong here
TACACS+ is used for device management, not subscriber authentication.
Visual reference
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.