The answer is a missing `authentication command bounce-port` or `authentication command disable-port` configuration on the switch. When performing Change of Authorization CoA troubleshooting for a VLAN change failure, the switch must be explicitly told how to apply the new authorization state. Without these commands, the switch acknowledges the CoA request but lacks the instruction to reinitialize the port, so the existing VLAN assignment remains unchanged. On the ENCOR 350-401 exam, this scenario tests your understanding that CoA is a two-step process: the switch must both accept the request and have a method to enforce the change. A common trap is assuming a successful “CoA request received” log means the VLAN updated, but the switch only processes the request—it does not act without the bounce-port or disable-port directive. Remember the memory tip: “Acknowledge is not action—bounce the port to bounce the VLAN.”
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.
A network engineer is deploying 802.1X with Cisco ISE for a wired network. The engineer wants to use CoA (Change of Authorization) to dynamically change the VLAN of a user after authentication. The engineer configures the switch with 'aaa server radius dynamic-author' and the ISE with CoA settings. When the engineer tests CoA from ISE, the switch logs show 'CoA request received' but the VLAN does not change. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The switch is missing the 'authentication command bounce-port' or 'authentication command disable-port' configuration.
CoA requires the switch to accept and process the request. The switch must have the 'authentication command bounce-port' or 'authentication command disable-port' configured to apply changes. Option B is correct because without this, the switch may acknowledge but not act. Option A is incorrect because the switch received the request. Option C is incorrect because the RADIUS server is reachable. Option D is incorrect because the switchport mode does not prevent CoA.
Key principle: Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
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 ISE is not configured with the correct shared secret for CoA.
Why it's wrong here
Incorrect because the switch received the request, indicating shared secret is correct.
✓
The switch is missing the 'authentication command bounce-port' or 'authentication command disable-port' configuration.
Why this is correct
Correct because these commands enable the switch to apply CoA actions like VLAN change.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Authentication checks who the user is.
✗
The switch is not configured with 'dot1x pae authenticator' on the interface.
Why it's wrong here
Incorrect because 802.1X is already working; CoA is a separate feature.
✗
The switchport is configured as 'switchport mode trunk', which does not support VLAN changes via CoA.
Why it's wrong here
Incorrect because CoA can change VLAN on trunk ports as well.
Common exam traps
Common exam trap: authentication is not authorization
Logging in proves the user can authenticate. It does not automatically mean the user is allowed to enter privileged or configuration mode. Watch for AAA authorization, privilege level and command authorization details.
Detailed technical explanation
How to think about this question
This kind of question is testing the difference between identity and permission. A user may successfully log in to a router because authentication is working, but still fail to enter configuration mode because authorization is missing, misconfigured or mapped to a lower privilege level.
KKey Concepts to Remember
Authentication checks who the user is.
Authorization controls what the user is allowed to do after login.
Privilege levels affect access to EXEC and configuration commands.
AAA, TACACS+ and RADIUS can separate login success from command access.
TExam Day Tips
→Do not assume successful login means full administrative access.
→Look for words such as cannot enter configuration mode, privilege level, authorization or command access.
→Separate login problems from permission problems before choosing the answer.
Key takeaway
Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
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 Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related 350-401 questions on access control and AAA configuration.
802.1X and TrustSec — This question tests 802.1X and TrustSec — Authentication checks who the user is..
What is the correct answer to this question?
The correct answer is: The switch is missing the 'authentication command bounce-port' or 'authentication command disable-port' configuration. — CoA requires the switch to accept and process the request. The switch must have the 'authentication command bounce-port' or 'authentication command disable-port' configured to apply changes. Option B is correct because without this, the switch may acknowledge but not act. Option A is incorrect because the switch received the request. Option C is incorrect because the RADIUS server is reachable. Option D is incorrect because the switchport mode does not prevent CoA.
What should I do if I get this 350-401 question wrong?
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related 350-401 questions on access control and AAA configuration.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Authentication checks who the user is.
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