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350-401 Practice Question: Which two statements about 802.1X authentication…
Which two statements about 802.1X authentication with MAC Authentication Bypass (MAB) are true? (Choose two.)
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
✓
MAB is used as a fallback authentication method for devices that do not support 802.1X.
MAB is used as a fallback for devices that do not support 802.1X supplicant, and it uses the MAC address as the credential. Option A is correct because MAB is typically configured as a fallback method. Option C is correct because the MAC address is used as both username and password. Option B is incorrect because MAB does not use certificates; that is for EAP-TLS. Option D is incorrect because MAB sends the MAC address in the clear, not encrypted. Option E is incorrect because MAB does not use EAPoL; it uses RADIUS with the MAC address.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
MAB is used as a fallback authentication method for devices that do not support 802.1X.
Why this is correct
Correct; MAB allows non-802.1X-capable devices to authenticate.
- ✗
MAB requires the supplicant to present a digital certificate for authentication.
Why it's wrong here
Incorrect; MAB uses MAC addresses, not certificates.
- ✓
In MAB, the switch sends the MAC address of the endpoint as the username and password to the RADIUS server.
Why this is correct
Correct; the MAC address is used as both the username and password in the RADIUS request.
- ✗
MAB encrypts the MAC address using TLS before sending it to the RADIUS server.
Why it's wrong here
Incorrect; MAB sends the MAC address in plaintext within the RADIUS packet.
- ✗
MAB uses EAPoL to transport the MAC address between the switch and the endpoint.
Why it's wrong here
Incorrect; MAB does not involve EAPoL; the switch directly sends a RADIUS Access-Request.
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 Access Control and AAA
Key term
MAB Authentication
MAB Authentication is a network access control method that grants or denies device access to a network by checking the device's MAC address against a list of approved addresses.
Key term
Cisco TrustSec
Cisco TrustSec is a security architecture that uses identity-based access control and encryption to protect network traffic, rather than relying only on IP addresses and VLANs.
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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.