Question 748 of 2,152

DHCP (IPv4 and IPv6) →hardMultiple ChoiceObjective-mapped

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.

An engineer configures DHCPv4 on a router with multiple pools for different subnets. Clients in subnet A receive addresses correctly, but clients in subnet B receive addresses from subnet A's pool. The router has 'ip dhcp relay' configured. 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.

A
The DHCP server selects the pool based on the giaddr; if the relay agent does not set the giaddr correctly, the server may use the first matching pool.
Correct: The giaddr is critical for pool selection. If it is not set (e.g., due to missing 'ip helper-address' on the correct interface), the server may assign from a different pool.
B
The pools are configured in the wrong order; the server uses the first pool that matches the client's MAC address.
Why wrong: Incorrect: Pool selection is based on giaddr, not MAC address, unless using manual bindings.
C
The router has 'ip dhcp smart-relay' enabled, which overrides pool selection.
Why wrong: Incorrect: Smart relay is a feature that helps with giaddr, but it does not cause wrong pool selection.
D
The DHCP server is configured with 'network' statements that overlap.
Why wrong: Incorrect: Overlapping networks would cause conflicts, but the symptom is specific to subnet B getting addresses from subnet A.

Full breakdown with real-world context →

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 selects the pool based on the giaddr; if the relay agent does not set the giaddr correctly, the server may use the first matching pool.

Option A is correct because when a DHCP relay agent forwards a client's request to the server, it inserts its own IP address (the interface address on the client's subnet) into the giaddr (gateway IP address) field. The DHCP server uses this giaddr to select the appropriate pool. If the relay agent fails to set the giaddr correctly—for example, due to misconfiguration or the relay interface not being on the correct subnet—the server may receive a giaddr of 0.0.0.0 or an incorrect address, causing it to fall back to the first configured pool that matches, which in this case is subnet A's 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 server selects the pool based on the giaddr; if the relay agent does not set the giaddr correctly, the server may use the first matching pool.
Why this is correct
Correct: The giaddr is critical for pool selection. If it is not set (e.g., due to missing 'ip helper-address' on the correct interface), the server may assign from a different pool.
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 pools are configured in the wrong order; the server uses the first pool that matches the client's MAC address.
Why it's wrong here
Incorrect: Pool selection is based on giaddr, not MAC address, unless using manual bindings.
✗
The router has 'ip dhcp smart-relay' enabled, which overrides pool selection.
Why it's wrong here
Incorrect: Smart relay is a feature that helps with giaddr, but it does not cause wrong pool selection.
✗
The DHCP server is configured with 'network' statements that overlap.
Why it's wrong here
Incorrect: Overlapping networks would cause conflicts, but the symptom is specific to subnet B getting addresses from subnet A.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Cisco often tests the misconception that DHCP pool selection is based on pool order or client MAC address, when in fact it relies on the giaddr set by the relay agent.

Detailed technical explanation

How to think about this question

The giaddr field is defined in RFC 2131 and is critical for DHCP relay operation; without a correct giaddr, the server cannot determine which subnet the client belongs to. In Cisco IOS, the 'ip helper-address' command enables DHCP relay, and the relay agent automatically sets the giaddr to the IP address of the interface receiving the client's DHCPDISCOVER. A common real-world misconfiguration is when the relay interface is in a VRF or has a secondary IP address that does not match the client's subnet, causing the giaddr to be set incorrectly and leading to pool misassignment.

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 network engineer segments a warehouse floor into three subnets: 20 scanners, 5 printers, and 2 management hosts. Picking the wrong mask wastes addresses or leaves too few usable hosts. Exam questions test whether you can apply CIDR notation, calculate block size, and identify the correct usable-host range for a given prefix.

Visual reference

What to study next

Got this wrong? Here's your next step.

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

Related 300-410 practice-question pages

Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.

Layer 3 Technologies practice questions

Practise 300-410 questions linked to Layer 3 Technologies.

EIGRP Troubleshooting practice questions

Practise 300-410 questions linked to EIGRP Troubleshooting.

OSPF Troubleshooting (v2/v3) practice questions

Practise 300-410 questions linked to OSPF Troubleshooting (v2/v3).

BGP Troubleshooting practice questions

Practise 300-410 questions linked to BGP Troubleshooting.

Route Redistribution practice questions

Practise 300-410 questions linked to Route Redistribution.

Policy-Based Routing (PBR) practice questions

Practise 300-410 questions linked to Policy-Based Routing (PBR).

VRF-Lite practice questions

Practise 300-410 questions linked to VRF-Lite.

Route Maps and Route Filtering practice questions

Practise 300-410 questions linked to Route Maps and Route Filtering.

Administrative Distance practice questions

Practise 300-410 questions linked to Administrative Distance.

Route Summarization practice questions

Practise 300-410 questions linked to Route Summarization.

Bidirectional Forwarding Detection (BFD) practice questions

Practise 300-410 questions linked to Bidirectional Forwarding Detection (BFD).

VPN Technologies practice questions

Practise 300-410 questions linked to VPN Technologies.

Practice this exam

Start a free 300-410 practice session

Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.

10 questions 20 questions 30 questions 50 questions Timed 30

300-410 practice-test guide →Study guide →Browse all practice tests

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 server selects the pool based on the giaddr; if the relay agent does not set the giaddr correctly, the server may use the first matching pool. — Option A is correct because when a DHCP relay agent forwards a client's request to the server, it inserts its own IP address (the interface address on the client's subnet) into the giaddr (gateway IP address) field. The DHCP server uses this giaddr to select the appropriate pool. If the relay agent fails to set the giaddr correctly—for example, due to misconfiguration or the relay interface not being on the correct subnet—the server may receive a giaddr of 0.0.0.0 or an incorrect address, causing it to fall back to the first configured pool that matches, which in this case is subnet A's 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.

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 →

How Courseiva writes practice questions · Editorial policy

Keep practising

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.

Loading comments…

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.