- A
The DHCP server is not configured to trust the relay agent information option (option 82), causing it to discard the requests.
Correct: By default, DHCP snooping inserts option 82. Many servers reject packets with option 82 unless configured to trust it.
- B
The trusted port is in the wrong VLAN; DHCP snooping only works when the trusted port is in the same VLAN as the clients.
Why wrong: Incorrect: The trusted port can be in any VLAN; DHCP snooping operates per VLAN.
- C
The switch has 'ip dhcp snooping verify mac-address' enabled, causing MAC address mismatches.
Why wrong: Incorrect: This feature checks the source MAC in the DHCP packet against the Ethernet header, but the issue is about option 82.
- D
The DHCP server is not configured with the correct subnet for the client VLAN.
Why wrong: Incorrect: This would cause server-side issues, but the symptom is that no clients get addresses, and the server is reachable.
300-410 DHCP (IPv4 and IPv6) Practice Question
This 300-410 practice question tests your understanding of dhcp (ipv4 and ipv6). The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 configures a DHCP snooping trusted port on a switch to allow a legitimate DHCP server. However, clients connected to untrusted ports on the same VLAN cannot obtain IP addresses. The DHCP server is reachable and the switch shows no DHCP snooping drops. Which is the most likely explanation?
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 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 DHCP server is not configured to trust the relay agent information option (option 82), causing it to discard the requests.
DHCP snooping requires IP source guard or DHCP snooping binding to be populated. If the switch has 'ip dhcp snooping information option' enabled, the DHCP server may drop packets due to option 82 being inserted, unless the server is configured to trust it.
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.
- ✓
The DHCP server is not configured to trust the relay agent information option (option 82), causing it to discard the requests.
Why this is correct
Correct: By default, DHCP snooping inserts option 82. Many servers reject packets with option 82 unless configured to trust it.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Access ports place end devices into a single VLAN.
- ✗
The trusted port is in the wrong VLAN; DHCP snooping only works when the trusted port is in the same VLAN as the clients.
Why it's wrong here
Incorrect: The trusted port can be in any VLAN; DHCP snooping operates per VLAN.
- ✗
The switch has 'ip dhcp snooping verify mac-address' enabled, causing MAC address mismatches.
Why it's wrong here
Incorrect: This feature checks the source MAC in the DHCP packet against the Ethernet header, but the issue is about option 82.
- ✗
The DHCP server is not configured with the correct subnet for the client VLAN.
Why it's wrong here
Incorrect: This would cause server-side issues, but the symptom is that no clients get addresses, and the server is reachable.
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.
What to study next
Got this wrong? Here's your next step.
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 300-410 questions on switching, trunking, and access-port configuration.
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FAQ
Questions learners often ask
What does this 300-410 question test?
DHCP (IPv4 and IPv6) — This question tests DHCP (IPv4 and IPv6) — Access ports place end devices into a single VLAN..
What is the correct answer to this question?
The correct answer is: The DHCP server is not configured to trust the relay agent information option (option 82), causing it to discard the requests. — DHCP snooping requires IP source guard or DHCP snooping binding to be populated. If the switch has 'ip dhcp snooping information option' enabled, the DHCP server may drop packets due to option 82 being inserted, unless the server is configured to trust it.
What should I do if I get this 300-410 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 300-410 questions on switching, trunking, and access-port 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?
Access ports place end devices into a single VLAN.
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Last reviewed: Jun 19, 2026
This 300-410 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 300-410 exam.
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