The answer is configuring 'authentication host-mode multi-domain' on the interface. This is the most likely cause of the failure because in an 802.1X voice VLAN deployment, the switchport defaults to single-host mode, which only permits one authenticated device per port. Multi-domain host mode is required to allow two separate authentication domains—one for the IP phone (voice device) and one for the PC behind it (data device)—enabling the phone to receive the voice VLAN and transition to an authenticated state. On the CCNA 200-301 v2 exam, this tests your understanding of how 802.1X interacts with voice VLANs, a common trap being that candidates forget to change the host mode from the default single-host. A reliable memory tip is "two domains, two devices"—multi-domain for phone and PC, single-domain for just one device.
CCNA Network Services and Security Practice Question
This 200-301 practice question tests your understanding of network services and security. 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.
Exhibit
Interface: GigabitEthernet1/0/1
MAC Address: aaaa.bbbb.cccc
IP Address: Unknown
Status: Authz Success
Domain: DATA
Oper host mode: single-host
Oper control dir: both
Session timeout: N/A
Common Session ID: 0A1B2C3D4E5F6G7H8I9J
Acct Session ID: 0x00000001
Handle: 0x81000001
Current Policy: DEFAULT
Server Policies:
Vlan Group: Vlan: 10
Method status list:
Method State
dot1x Authc Success
An engineer configures 802.1X port-based authentication on a Cisco IOS-XE switch for a voice VLAN deployment. After applying the configuration, IP phones on interface GigabitEthernet1/0/1 fail to receive a voice VLAN and remain in an unauthenticated state. The switchport is configured as an access port with voice VLAN 10. What is the most likely cause of the failure?
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
✓
Configure 'authentication host-mode multi-domain' on the interface
The correct answer is B because in a voice VLAN deployment with 802.1X, the switchport must be configured with 'authentication host-mode multi-domain' to allow both a data device (phone) and a voice device (PC behind the phone) to authenticate separately. Without this mode, the port defaults to single-host mode, which prevents the phone from receiving the voice VLAN and keeps it in an unauthenticated state.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Re-authenticate the phone using 'dot1x reauthenticate interface Gi1/0/1'
Why it's wrong here
Re-authentication would not change the domain assignment because the port is still in single-host mode.
✓
Configure 'authentication host-mode multi-domain' on the interface
Why this is correct
This command allows the switch to authorize both data and voice domains separately on the same port, enabling the phone to receive the voice VLAN.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Add 'switchport voice vlan 10' under the interface
Why it's wrong here
The voice VLAN is already configured; the issue is not the VLAN assignment but the authentication domain.
✗
Change the port to 'authentication port-control force-authorized'
Why it's wrong here
This would bypass 802.1X entirely, which is not desired for a secure deployment and would not resolve the domain issue.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓Configure 'authentication host-mode multi-domain' on the interfaceCorrect answer▾
Why this is correct
This command allows the switch to authorize both data and voice domains separately on the same port, enabling the phone to receive the voice VLAN.
✗Re-authenticate the phone using 'dot1x reauthenticate interface Gi1/0/1'Wrong answer — click to see why▾
Why this is wrong here
Re-authentication forces the phone to re-authenticate, but the port remains in single-host mode, which only allows one authenticated device. The phone's data and voice domains are not separated, so the voice VLAN assignment still fails.
Why candidates choose this
Students may think re-authentication will refresh the session and correct the VLAN assignment, but the underlying host-mode issue persists.
✗Add 'switchport voice vlan 10' under the interfaceWrong answer — click to see why▾
Why this is wrong here
The voice VLAN is already configured with 'switchport voice vlan 10' as stated in the scenario. The issue is not the VLAN definition but the authentication domain separation; the phone remains unauthenticated because the port cannot assign the voice VLAN without proper multi-domain support.
Why candidates choose this
A common troubleshooting step is to verify voice VLAN configuration, but since it is already present, this option is a distractor that tests attention to detail.
✗Change the port to 'authentication port-control force-authorized'Wrong answer — click to see why▾
Why this is wrong here
Setting 'authentication port-control force-authorized' bypasses 802.1X authentication entirely, which defeats the purpose of port-based security. It would allow the phone to connect without authentication, but the voice VLAN assignment still requires proper domain handling; moreover, this is not a secure solution.
Why candidates choose this
Students might consider force-authorizing as a quick fix to allow the phone to work, but it ignores the authentication requirement and does not address the root cause of domain separation.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume the issue is a missing voice VLAN command or an authentication failure, but Cisco specifically tests the requirement for multi-domain host mode when voice VLAN is used with 802.1X.
Detailed technical explanation
How to think about this question
Under the hood, 802.1X with multi-domain host mode allows the switch to maintain separate authentication states for the voice domain (phone) and data domain (PC), enabling the voice VLAN to be dynamically assigned via RADIUS attributes (e.g., Cisco AV-pair 'device-traffic-class=voice'). In single-host mode, the switch expects only one authenticated device, so the phone's voice VLAN request is ignored, leaving it in an unauthenticated state. This is a common scenario in Cisco IP telephony deployments where the phone acts as a bridge for a PC.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 200-301 question in full detail.
Network Services and Security — This question tests Network Services and Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Configure 'authentication host-mode multi-domain' on the interface — The correct answer is B because in a voice VLAN deployment with 802.1X, the switchport must be configured with 'authentication host-mode multi-domain' to allow both a data device (phone) and a voice device (PC behind the phone) to authenticate separately. Without this mode, the port defaults to single-host mode, which prevents the phone from receiving the voice VLAN and keeps it in an unauthenticated state.
What should I do if I get this 200-301 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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?
Read the scenario before looking for a memorised answer.
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