350-701 Practice Question: Secure Network Access, Visibility and Enforcement
A network engineer notices that some Windows 10 clients fail to authenticate via 802.1X after a recent OS update. The supplicant shows 'EAPOL-Start' but never receives an EAP-Request/Identity. The switch port is configured with 'authentication port-control auto' and 'dot1x pae authenticator'. What is the most likely cause?
⚠ Common exam trap
Cisco often tests the misconception that 802.1X can work on any port type, but the trap here is that 802.1X is only supported on access ports, and trunk ports will silently ignore EAPOL-Start frames.
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
✓
The switch port is configured as a trunk port
The most likely cause is that the switch port is configured as a trunk port. 802.1X authentication is designed for access ports, not trunk ports. On a trunk port, the switch does not process EAPOL frames correctly because the port is expected to carry multiple VLANs and the switch's 802.1X state machine does not initiate the authentication process. As a result, the supplicant sends EAPOL-Start but the switch never responds with an EAP-Request/Identity, leading to authentication failure.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The switch port is configured as a trunk port
Why this is correct
802.1X is not supported on trunk ports by default. The switch will not respond to EAPOL-Start on trunk ports.
- ✗
The switch has 'aaa authentication dot1x default none' globally
Why it's wrong here
This would allow all without authentication, but the switch would still respond to EAPOL.
- ✗
The switch port is configured with 'authentication order mab dot1x'
Why it's wrong here
MAB is a fallback method and does not prevent the switch from responding to EAPOL.
- ✗
The switch is configured with 'snmp-server community' which disables 802.1X
Why it's wrong here
SNMP does not affect EAPOL processing.
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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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 350-701 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 350-701 exam.