- A
DHCP snooping
Why wrong: DHCP snooping filters DHCP messages to prevent rogue DHCP servers, but it does not restrict which MAC addresses can connect to a port.
- B
Dynamic ARP inspection
Why wrong: DAI validates ARP packets to prevent ARP spoofing, but it does not control which MAC addresses are allowed on a port.
- C
Port security
Correct. Port security limits the MAC addresses that can communicate through a switch port, preventing unauthorized devices from connecting.
- D
802.1X
Why wrong: 802.1X provides network access control by authenticating users or devices before granting access, but it relies on a RADIUS server and does not specifically restrict based on MAC addresses alone.
Question 192 of 520
How to Block Unauthorized Devices with Port Security
This N10-009 practice question tests your understanding of network security. 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.
A network administrator wants to prevent unauthorized devices from being plugged into switch ports. Only devices with specific MAC addresses should be allowed on each port. Which switch security feature should be enabled?
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
✓
Port security
Port security is the correct feature because it allows the administrator to restrict which MAC addresses can communicate through a switch port. By configuring allowed MAC addresses (sticky or static), any device with an unknown MAC address attempting to send traffic will trigger a security violation (shutdown, restrict, or protect). This directly addresses the requirement to prevent unauthorized devices from being plugged into switch ports.
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.
- ✗
DHCP snooping
Why it's wrong here
DHCP snooping filters DHCP messages to prevent rogue DHCP servers, but it does not restrict which MAC addresses can connect to a port.
When this WOULD be correct
A network administrator wants to prevent rogue DHCP servers from offering IP addresses to clients on a specific VLAN. DHCP snooping should be enabled on the switch to filter DHCP messages and only allow DHCP responses from trusted ports.
- ✗
Dynamic ARP inspection
Why it's wrong here
DAI validates ARP packets to prevent ARP spoofing, but it does not control which MAC addresses are allowed on a port.
When this WOULD be correct
A network administrator wants to prevent man-in-the-middle attacks by ensuring that only valid ARP responses are accepted on a VLAN. DAI should be enabled to drop ARP packets with invalid IP-to-MAC address bindings.
- ✓
Port security
Why this is correct
Correct. Port security limits the MAC addresses that can communicate through a switch port, preventing unauthorized devices from connecting.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
802.1X
Why it's wrong here
802.1X provides network access control by authenticating users or devices before granting access, but it relies on a RADIUS server and does not specifically restrict based on MAC addresses alone.
When this WOULD be correct
A question asks: 'A company wants to ensure that only authenticated users can connect to the network, using their domain credentials. Which switch security feature should be enabled?' In that scenario, 802.1X would be correct.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The N10-009 exam frequently reuses these exact scenarios with slightly different constraints.
✓Port securityCorrect answer▾
Why this is correct
Correct. Port security limits the MAC addresses that can communicate through a switch port, preventing unauthorized devices from connecting.
✗DHCP snoopingWrong answer — click to see why▾
Why this is wrong here
DHCP snooping is a security feature that filters untrusted DHCP messages and builds a DHCP snooping binding table, but it does not restrict which devices can be plugged into switch ports based on MAC addresses.
★ When this WOULD be the correct answer
A network administrator wants to prevent rogue DHCP servers from offering IP addresses to clients on a specific VLAN. DHCP snooping should be enabled on the switch to filter DHCP messages and only allow DHCP responses from trusted ports.
Why candidates choose this
Candidates may confuse DHCP snooping with port security because both involve MAC addresses; DHCP snooping tracks MAC-to-IP bindings, leading to the mistaken belief it can enforce MAC-based port access.
✗Dynamic ARP inspectionWrong answer — click to see why▾
Why this is wrong here
Dynamic ARP inspection (DAI) validates ARP packets to prevent ARP spoofing attacks, but it does not restrict which devices can be physically plugged into switch ports based on MAC addresses.
★ When this WOULD be the correct answer
A network administrator wants to prevent man-in-the-middle attacks by ensuring that only valid ARP responses are accepted on a VLAN. DAI should be enabled to drop ARP packets with invalid IP-to-MAC address bindings.
Why candidates choose this
Candidates may confuse DAI's use of MAC addresses for validation with port security's MAC address filtering, or think that any feature involving MAC addresses can restrict physical port access.
✗802.1XWrong answer — click to see why▾
Why this is wrong here
802.1X is a port-based network access control protocol that authenticates users or devices before granting network access, but it does not restrict specific MAC addresses per port; it relies on authentication credentials, not a static MAC address list.
★ When this WOULD be the correct answer
A question asks: 'A company wants to ensure that only authenticated users can connect to the network, using their domain credentials. Which switch security feature should be enabled?' In that scenario, 802.1X would be correct.
Why candidates choose this
Candidates may confuse MAC-based authentication (which 802.1X can use) with port security's static MAC address filtering, or think 802.1X can enforce MAC address lists when it typically uses RADIUS-based authentication.
Analysis generated from the official N10-009blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
CompTIA often tests the distinction between port security (MAC-based access control) and 802.1X (authentication-based access control), leading candidates to incorrectly choose 802.1X when the question explicitly mentions 'specific MAC addresses' rather than user credentials or certificates.
Detailed technical explanation
How to think about this question
Port security operates by limiting the number of MAC addresses allowed on a port (default is 1) and can be configured with sticky MAC addresses that dynamically learn and save allowed MACs to the running config. When a violation occurs, the port can be placed in err-disabled state (shutdown mode), which requires manual or automatic recovery via errdisable recovery cause psecure-violation. In real-world scenarios, this is commonly used on access ports in conference rooms or public areas to prevent rogue devices from connecting to the network.
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 N10-009 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.
Quick reference
Access Control Model Comparison
| Model | Acronym | Who Controls Access? | Best For |
|---|---|---|---|
| Discretionary Access Control | DAC | Resource owner | Small teams, file shares |
| Mandatory Access Control | MAC | System / security labels | Classified govt / military |
| Role-Based Access Control | RBAC | Administrator (via roles) | Enterprise environments |
| Attribute-Based Access Control | ABAC | Policy engine (user + resource attributes) | Fine-grained, dynamic policies |
| Rule-Based Access Control | RuBAC | System rules / ACLs | Firewall rules, network ACLs |
What to study next
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FAQ
Questions learners often ask
What does this N10-009 question test?
Network Security — This question tests Network Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Port security — Port security is the correct feature because it allows the administrator to restrict which MAC addresses can communicate through a switch port. By configuring allowed MAC addresses (sticky or static), any device with an unknown MAC address attempting to send traffic will trigger a security violation (shutdown, restrict, or protect). This directly addresses the requirement to prevent unauthorized devices from being plugged into switch ports.
What should I do if I get this N10-009 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
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 →
Same concept, more angles
2 more ways this is tested on N10-009
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A network administrator wants to ensure that only authorized devices can access the network on a switch port. The administrator has a list of allowed MAC addresses. Which security feature should be enabled on the switch port?
medium- A.802.1X
- B.MAC address filtering
- ✓ C.Port security
- D.VLAN hopping prevention
Why C: Port security is the correct feature because it allows the administrator to specify a list of allowed MAC addresses per switch port. When a device with an unauthorized MAC address attempts to connect, the switch can either block the traffic, generate an alert, or disable the port (errdisable state). This directly enforces access control based on the MAC address list provided.
Variation 2. A network administrator wants to prevent unauthorized devices from connecting to the network by limiting the number of MAC addresses allowed on a switch port. Which security feature should be configured?
medium- A.802.1X
- ✓ B.Port security
- C.DHCP snooping
- D.Dynamic ARP inspection
Why B: Port security is the correct feature because it directly restricts the number of unique MAC addresses that can be learned on a switch port, preventing unauthorized devices from connecting. When the configured limit is exceeded, the switch can take actions such as shutdown, restrict, or protect, effectively blocking the unauthorized device. This is a Layer 2 access control mechanism that operates on the switch port itself.
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Last reviewed: Jun 30, 2026
This N10-009 practice question is part of Courseiva's free CompTIA 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 N10-009 exam.
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