The correct statement is that 802.1X will be attempted first, and if the client does not respond, MAB will be used as a fallback. This is because the `authentication port-control auto` command places the port in an unauthorized state by default, and the switch, configured as a dot1x authenticator, sends an EAP-Request Identity frame. If no 802.1X-capable device responds within the `dot1x timeout tx-period` of 10 seconds, the switch then falls back to MAB, using the source MAC address for authentication. On the ENCOR 350-401 exam, this tests your understanding of the default fallback order in Cisco’s Identity-Based Networking Services (IBNS) 2.0, where 802.1X always takes precedence unless explicitly reordered with the `authentication order` command. A common trap is assuming MAB runs first because it appears first in the config; in reality, the CLI order does not dictate the fallback sequence. Remember the mnemonic: “X before MAB” — 802.1X (eXtensible) is tried before MAC Authentication Bypass.
350-401 802.1X and TrustSec Practice Question
This 350-401 practice question tests your understanding of 802.1x and trustsec. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
802.1X will be attempted first; if the client does not respond, MAB will be used as a fallback.
This configuration enables both 802.1X and MAB (MAC Authentication Bypass) on the interface. MAB is used as a fallback if the connected device does not support 802.1X. The switch acts as an authenticator.
Key principle: A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
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 will be attempted first, and if it fails, 802.1X will be used.
Why it's wrong here
By default, 802.1X is attempted first; MAB is a fallback method.
✓
802.1X will be attempted first; if the client does not respond, MAB will be used as a fallback.
Why this is correct
The switch tries 802.1X first; if no EAPOL is received, it falls back to MAB.
Related concept
Access ports place end devices into a single VLAN.
✗
The port will be placed in a guest VLAN if both 802.1X and MAB fail.
The switch will act as a supplicant for MAB and an authenticator for 802.1X.
Why it's wrong here
The switch is configured as an authenticator for both methods.
Common exam traps
Common exam trap: an active trunk can still block the VLAN you need
A trunk being up does not prove every VLAN is crossing it. Check allowed VLAN lists, native VLAN mismatch, VLAN existence and access-port assignment.
Detailed technical explanation
How to think about this question
VLAN questions usually combine access-port and trunking clues. The key is to identify whether the issue is local to one switchport, caused by the trunk, or caused by the VLAN not existing where it needs to exist.
KKey Concepts to Remember
Access ports place end devices into a single VLAN.
Trunk ports carry multiple VLANs between switches.
Allowed VLAN lists decide which VLANs can cross a trunk.
Native VLAN mismatch can create confusing symptoms.
TExam Day Tips
→Use show vlan brief to verify access VLANs.
→Use show interfaces trunk to verify trunk state and allowed VLANs.
→Do not treat every same-VLAN issue as a routing problem.
Key takeaway
A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
Real-world example
How this comes up in practice
A help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 350-401 question in full detail.
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 350-401 questions on switching, trunking, and access-port configuration.
802.1X and TrustSec — This question tests 802.1X and TrustSec — Access ports place end devices into a single VLAN..
What is the correct answer to this question?
The correct answer is: 802.1X will be attempted first; if the client does not respond, MAB will be used as a fallback. — This configuration enables both 802.1X and MAB (MAC Authentication Bypass) on the interface. MAB is used as a fallback if the connected device does not support 802.1X. The switch acts as an authenticator.
What should I do if I get this 350-401 question wrong?
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 350-401 questions on switching, trunking, and access-port configuration.
What is the key concept behind this question?
Access ports place end devices into a single VLAN.
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