- A
The DHCP pool is configured under a VRF, but the interface is not in that VRF.
Correct because if the pool is defined with 'vrf <name>', it will only respond to DHCP requests on interfaces belonging to that VRF; the subinterface is not in any VRF, so the pool is ignored.
- B
The subinterface is missing the 'ip helper-address' command.
Why wrong: Incorrect because the router is the DHCP server, so helper-address is not needed; the server responds directly to DISCOVER messages on the same subnet.
- C
The 'ip dhcp server' command is missing globally.
Why wrong: Incorrect because the DHCP server process is enabled by default when a pool is configured; no global command is needed.
- D
The encapsulation dot1Q 10 is misconfigured, causing the router to not receive broadcasts.
Why wrong: Incorrect because if the subinterface were misconfigured, it would not be up/up; the engineer would see the interface status as down.
Quick Answer
The answer is a DHCP VRF pool and interface VRF mismatch. When a DHCP pool is configured under a specific VRF using the `vrf` command, the router will only respond to DISCOVER messages received on interfaces that belong to that same VRF; if the client-facing interface, such as Gi0/0.10, is not assigned to that VRF, the router silently drops the broadcasts, even if the subnet and gateway match the pool. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding of VRF-aware DHCP services, a common trap where engineers assume a matching IP subnet alone guarantees a lease. The key insight is that VRF isolation overrides subnet matching—the router treats the pool as invisible to interfaces outside its VRF. Memory tip: "Pool and port must be in the same VRF court."
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 is troubleshooting a DHCPv4 issue where a router configured as a DHCP server is not assigning addresses from a pool to clients on a specific VLAN. The pool is configured with 'network 10.1.1.0 255.255.255.0' and 'default-router 10.1.1.1'. The router's interface Gi0/0.10 (subinterface) has encapsulation dot1Q 10 and IP 10.1.1.1/24. Clients send DISCOVER messages, but the router does not respond. The engineer notices that the router has multiple DHCP pools configured. 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 DHCP pool is configured under a VRF, but the interface is not in that VRF.
The router has multiple DHCP pools configured, and the pool for VLAN 10 is likely bound to a VRF. When a DHCP pool is configured under a VRF, the router only responds to DHCP DISCOVER messages received on interfaces that belong to that same VRF. Since the subinterface Gi0/0.10 is not in the VRF, the router ignores the client broadcasts, even though the IP address and subnet match the pool.
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.
- ✓
The DHCP pool is configured under a VRF, but the interface is not in that VRF.
Why this is correct
Correct because if the pool is defined with 'vrf <name>', it will only respond to DHCP requests on interfaces belonging to that VRF; the subinterface is not in any VRF, so the pool is ignored.
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.
- ✗
The subinterface is missing the 'ip helper-address' command.
Why it's wrong here
Incorrect because the router is the DHCP server, so helper-address is not needed; the server responds directly to DISCOVER messages on the same subnet.
- ✗
The 'ip dhcp server' command is missing globally.
Why it's wrong here
Incorrect because the DHCP server process is enabled by default when a pool is configured; no global command is needed.
- ✗
The encapsulation dot1Q 10 is misconfigured, causing the router to not receive broadcasts.
Why it's wrong here
Incorrect because if the subinterface were misconfigured, it would not be up/up; the engineer would see the interface status as down.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the VRF-aware DHCP concept by presenting a scenario where a DHCP server has multiple pools and clients are not getting addresses, leading candidates to incorrectly suspect missing helper addresses or global DHCP commands, when the real issue is a VRF mismatch between the pool and the interface.
Trap categories for this question
Command / output trap
Incorrect because the DHCP server process is enabled by default when a pool is configured; no global command is needed.
Detailed technical explanation
How to think about this question
In Cisco IOS, DHCP pools can be associated with a VRF using the 'vrf' command under the pool configuration. When a pool is VRF-aware, the DHCP server uses the VRF table to match incoming requests; the server will only respond if the incoming interface is in the same VRF. This is critical in MPLS or multi-tenant environments where overlapping address spaces exist, and it prevents address assignment to clients in the wrong VRF.
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.
What to study next
Got this wrong? Here's your next step.
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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) — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The DHCP pool is configured under a VRF, but the interface is not in that VRF. — The router has multiple DHCP pools configured, and the pool for VLAN 10 is likely bound to a VRF. When a DHCP pool is configured under a VRF, the router only responds to DHCP DISCOVER messages received on interfaces that belong to that same VRF. Since the subinterface Gi0/0.10 is not in the VRF, the router ignores the client broadcasts, even though the IP address and subnet match the pool.
What should I do if I get this 300-410 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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Last reviewed: Jun 24, 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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