- A
The router's interface is configured with the no ip forward-protocol udp bootps command.
Why wrong: Incorrect because that command would affect DHCP relay, not the local DHCP server.
- B
The router's interface is not in the same VLAN as the client, and no ip helper-address is configured.
Correct because if the router is not directly connected to the client's VLAN, the DHCP broadcast will not reach the router unless a DHCP relay (ip helper-address) is configured on the client's VLAN interface.
- C
The DHCP pool is configured with the wrong default-router option.
Why wrong: Incorrect because the default-router option is only sent in the DHCP offer; it does not affect whether the discover message is received.
- D
The router's DHCP server is disabled globally with the no service dhcp command.
Why wrong: Incorrect because if the DHCP server were disabled, no pool would be active, but the engineer would likely see an error message.
Quick Answer
The answer is that the router’s interface is in a different VLAN than the client, and no ip helper-address is configured. This is correct because DHCP client discovery messages are broadcast frames, and by default, routers do not forward broadcasts across VLAN boundaries. Without the ip helper-address command on the router’s interface facing the client’s VLAN, the DHCP server cannot receive the client’s request, even if the pool and excluded-address settings are correct. On the ENCOR 350-401 exam, this scenario tests your understanding of DHCP relay and Layer 3 broadcast forwarding—a common trap is assuming the server and client must be on the same subnet, when in reality the helper address bridges the VLAN gap. Remember the memory tip: “No helper, no handshake”—if the router lacks a helper address, the DHCP four-way handshake never starts.
CCNP NAT and DHCP Practice Question
This 350-401 practice question tests your understanding of nat and dhcp. 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 is troubleshooting a DHCP issue where a client is not receiving an IP address from a Cisco router configured as a DHCP server. The engineer checks the DHCP pool configuration and sees that the network command is configured with the correct subnet. The engineer also verifies that the ip dhcp excluded-address command is not blocking any addresses. However, the client's DHCP discover message is not reaching the router. 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 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 router's interface is not in the same VLAN as the client, and no ip helper-address is configured.
DHCP uses broadcast messages. If the router's interface is not configured to receive broadcasts (e.g., due to a switched network with VLANs), the DHCP server may not see the client's request. However, the most common issue is that the interface is not configured with the ip dhcp server command or the interface is in a different VLAN without a helper address.
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 router's interface is configured with the no ip forward-protocol udp bootps command.
Why it's wrong here
Incorrect because that command would affect DHCP relay, not the local DHCP server.
- ✓
The router's interface is not in the same VLAN as the client, and no ip helper-address is configured.
Why this is correct
Correct because if the router is not directly connected to the client's VLAN, the DHCP broadcast will not reach the router unless a DHCP relay (ip helper-address) is configured on the client's VLAN interface.
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 DHCP pool is configured with the wrong default-router option.
Why it's wrong here
Incorrect because the default-router option is only sent in the DHCP offer; it does not affect whether the discover message is received.
- ✗
The router's DHCP server is disabled globally with the no service dhcp command.
Why it's wrong here
Incorrect because if the DHCP server were disabled, no pool would be active, but the engineer would likely see an error message.
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.
Trap categories for this question
Command / output trap
Incorrect because that command would affect DHCP relay, not the local DHCP server.
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 350-401 questions on switching, trunking, and access-port configuration.
- →
NAT and DHCP — study guide chapter
Learn the concepts, then practise the questions
- →
NAT and DHCP practice questions
Targeted practice on this topic area only
- →
All 350-401 questions
2,015 questions across all exam domains
- →
ENCOR 350-401 study guide
Full concept coverage aligned to exam objectives
- →
350-401 practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related 350-401 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Architecture practice questions
Practise 350-401 questions linked to Architecture.
Enterprise Network Design practice questions
Practise 350-401 questions linked to Enterprise Network Design.
SD-Access Architecture practice questions
Practise 350-401 questions linked to SD-Access Architecture.
SD-WAN Architecture practice questions
Practise 350-401 questions linked to SD-WAN Architecture.
QoS Architecture practice questions
Practise 350-401 questions linked to QoS Architecture.
Virtualization practice questions
Practise 350-401 questions linked to Virtualization.
Network Function Virtualization practice questions
Practise 350-401 questions linked to Network Function Virtualization.
Virtual Machines and Hypervisors practice questions
Practise 350-401 questions linked to Virtual Machines and Hypervisors.
VRF and Path Isolation practice questions
Practise 350-401 questions linked to VRF and Path Isolation.
Infrastructure practice questions
Practise 350-401 questions linked to Infrastructure.
OSPF practice questions
Practise 350-401 questions linked to OSPF.
BGP practice questions
Practise 350-401 questions linked to BGP.
Practice this exam
Start a free 350-401 practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Questions learners often ask
What does this 350-401 question test?
NAT and DHCP — This question tests NAT and DHCP — Access ports place end devices into a single VLAN..
What is the correct answer to this question?
The correct answer is: The router's interface is not in the same VLAN as the client, and no ip helper-address is configured. — DHCP uses broadcast messages. If the router's interface is not configured to receive broadcasts (e.g., due to a switched network with VLANs), the DHCP server may not see the client's request. However, the most common issue is that the interface is not configured with the ip dhcp server command or the interface is in a different VLAN without a helper address.
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.
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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Last reviewed: Jun 18, 2026
This 350-401 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 350-401 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.