350-601 Security Practice Question
A data center engineer is configuring 802.1X authentication on Cisco Nexus switches for wired endpoints. The requirement is to allow traffic on the port even if no EAPOL packet is received from the endpoint (e.g., a printer). Which authentication method should be used?
⚠ Common exam trap
Cisco often tests the distinction between authentication methods that require EAPOL (802.1X) and those that do not (MAB), and the trap here is that candidates confuse port security or local authentication with network access control, failing to recognize that MAB is the specific fallback for non-EAPOL endpoints.
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
✓
MAC Authentication Bypass (MAB)
MAC Authentication Bypass (MAB) is the correct method because it allows a port to authenticate endpoints that do not send EAPOL frames, such as printers or other legacy devices. When no EAPOL is received within a configurable timeout, the switch falls back to using the source MAC address of the first frame as the authentication credential, sending it to the RADIUS server for verification. This satisfies the requirement to permit traffic even without 802.1X supplicant capability.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
MAC Authentication Bypass (MAB)
Why this is correct
MAB uses the device's MAC address to authenticate against the RADIUS server if no EAPOL is received.
- ✗
802.1X using RADIUS server
Why it's wrong here
802.1X requires EAPoL packets from the endpoint.
- ✗
Port security with sticky MAC addresses
Why it's wrong here
Port security does not provide authentication.
- ✗
Local authentication with a predefined list of users
Why it's wrong here
Local authentication still requires 802.1X or CLI login.
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 350-601 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 350-601 exam.