- A
A firewall on the client is blocking UDP port 67 (DHCP server).
DHCP uses UDP ports 67 and 68; blocking port 67 prevents the client from receiving DHCPOFFER messages.
- B
The DHCP server is configured with a different subnet than the client's broadcast domain.
Why wrong: Without a DHCP relay, the server would not receive requests; but if a relay is present, it can still assign addresses from a different subnet.
- C
The DHCP server's address pool is exhausted.
No available IP addresses means the client cannot obtain a lease.
- D
The DHCP server has MAC address filtering enabled and the client's MAC is not allowed.
MAC filtering prevents the client from receiving an IP address.
- E
The client interface is configured with a static IP address.
Why wrong: A static IP means the client is not using DHCP at all, so it won't attempt to obtain an address.
Quick Answer
The answer is that a client-side firewall blocking UDP port 67 is one of three conditions that can cause a Linux DHCP client to fail to obtain an IP address. This is correct because the DHCP protocol relies on UDP port 67 for server-to-client communication, specifically for delivering DHCPOFFER and DHCPACK messages; when a client firewall blocks inbound traffic on this port, the client never receives the server’s response, leaving it stuck in a DISCOVER loop without an assigned address. On the LPIC-2 exam, this scenario tests your understanding of DHCP packet flow and common misconfigurations, often appearing as a trap where candidates mistakenly blame the server or network instead of the client’s own firewall rules. A key memory tip is to remember that DHCP uses two ports: 67 for the server and 68 for the client—so if the client can’t hear the server, check port 67 first.
LPIC-2 Network Client Management Practice Question
This LPIC-2 practice question tests your understanding of network client management. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
Which THREE conditions can cause a Linux DHCP client to fail to obtain an IP address? (Select THREE.)
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
A firewall on the client is blocking UDP port 67 (DHCP server).
Option A is correct because a client-side firewall blocking UDP port 67 prevents the DHCP client from receiving DHCPOFFER and DHCPACK messages from the server. DHCP uses UDP ports 67 (server) and 68 (client); blocking port 67 on the client disrupts inbound server responses, causing the client to fail to obtain an IP address.
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.
- ✓
A firewall on the client is blocking UDP port 67 (DHCP server).
- ✗
The DHCP server is configured with a different subnet than the client's broadcast domain.
Why it's wrong here
Without a DHCP relay, the server would not receive requests; but if a relay is present, it can still assign addresses from a different subnet.
- ✓
The DHCP server's address pool is exhausted.
Why this is correct
No available IP addresses means the client cannot obtain a lease.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
The DHCP server has MAC address filtering enabled and the client's MAC is not allowed.
Why this is correct
MAC filtering prevents the client from receiving an IP address.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The client interface is configured with a static IP address.
Why it's wrong here
A static IP means the client is not using DHCP at all, so it won't attempt to obtain an address.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume a subnet mismatch (Option B) always prevents DHCP, but DHCP servers can offer addresses from different subnets if configured appropriately, and the client can accept them; the real failure condition is when the server cannot respond at all, such as with exhausted pools or MAC filtering.
Detailed technical explanation
How to think about this question
DHCP relies on UDP broadcasts (or unicasts after initial discovery) and the client's DHCP client daemon (e.g., dhclient, dhcpcd) listens on UDP port 68 for server responses. A firewall rule blocking inbound UDP 67 effectively drops all server replies, leaving the client in a DISCOVER/SELECTING state indefinitely. In practice, iptables rules like `-A INPUT -p udp --dport 67 -j DROP` would cause this failure, while the client's DHCPDISCOVER (source port 68) still reaches the server.
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.
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.
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FAQ
Questions learners often ask
What does this LPIC-2 question test?
Network Client Management — This question tests Network Client Management — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: A firewall on the client is blocking UDP port 67 (DHCP server). — Option A is correct because a client-side firewall blocking UDP port 67 prevents the DHCP client from receiving DHCPOFFER and DHCPACK messages from the server. DHCP uses UDP ports 67 (server) and 68 (client); blocking port 67 on the client disrupts inbound server responses, causing the client to fail to obtain an IP address.
What should I do if I get this LPIC-2 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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Last reviewed: Jun 11, 2026
This LPIC-2 practice question is part of Courseiva's free LPI 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 LPIC-2 exam.
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