- A
67
Port 67 is the DHCP server port, used to receive client requests and send offers.
- B
68
Why wrong: Port 68 is the DHCP client port, used by clients to send requests, but the question asks for server communication.
- C
53
Why wrong: Port 53 is DNS, not DHCP.
- D
123
Why wrong: Port 123 is NTP, used for time synchronization, not DHCP.
Question 883 of 1,020
DHCP Server Port 67 for CompTIA A+ 220-1201
This 220-1201 practice question tests your understanding of tcp & udp ports. 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 technician is troubleshooting a DHCP issue where clients are not receiving IP addresses. Which port must be open on the firewall for DHCP server communication?
Quick Answer
The answer is UDP port 67. This is the correct choice because the Dynamic Host Configuration Protocol (DHCP) server listens on UDP port 67 to receive client requests and send configuration data, while the client uses UDP port 68. When a firewall blocks port 67, the server cannot hear the DHCPDISCOVER broadcasts from clients, preventing IP address assignment entirely. On the CompTIA A+ Core 1 220-1201 exam, this concept tests your understanding of core network services and port numbers, often appearing in troubleshooting scenarios where clients fail to obtain an IP address. A common trap is confusing the server port (67) with the client port (68) or assuming DHCP uses TCP instead of UDP. To remember, think of the server as the “senior” port—67 is higher than 68, just as the server is above the client in the hierarchy.
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
✓
67
DHCP servers listen on UDP port 67 for incoming client requests (DHCPDISCOVER, DHCPREQUEST). For the server to receive these messages, the firewall must allow inbound traffic to port 67. Without this port open, the server cannot process client requests, and no IP addresses are assigned.
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.
- ✓
67
Why this is correct
Port 67 is the DHCP server port, used to receive client requests and send offers.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
68
Why it's wrong here
Port 68 is the DHCP client port, used by clients to send requests, but the question asks for server communication.
- ✗
53
- ✗
123
Common exam traps
Common exam trap: answer the scenario, not the keyword
A common misconception is that port 68 (the client port) is the server port, or that DHCP uses TCP instead of UDP, leading candidates to confuse the listening and response ports.
Detailed technical explanation
How to think about this question
DHCP uses a four-step handshake (DORA: Discover, Offer, Request, Acknowledge) where the server always listens on UDP 67. In a routed environment, DHCP relay agents (ip helper-address) forward client broadcasts to the server on port 67. A common subtlety is that the server's response uses a destination port of 68, but the initial inbound rule must permit port 67.
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 practitioner preparing for the 220-1201 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Visual reference
What to study next
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FAQ
Questions learners often ask
What does this 220-1201 question test?
TCP & UDP Ports — This question tests TCP & UDP Ports — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: 67 — DHCP servers listen on UDP port 67 for incoming client requests (DHCPDISCOVER, DHCPREQUEST). For the server to receive these messages, the firewall must allow inbound traffic to port 67. Without this port open, the server cannot process client requests, and no IP addresses are assigned.
What should I do if I get this 220-1201 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.
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Last reviewed: Jul 4, 2026
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