802.1X: Port-Based Network Access Control
A network administrator needs to ensure that only authorized devices can connect to the wired network. Each user must authenticate using their domain credentials. Which of the following should be implemented?
Quick Answer
The correct answer is 802.1X with EAP-TLS because it enforces port-based network access control, requiring each user to authenticate with domain credentials through a RADIUS server before the switch port opens for traffic. EAP-TLS provides mutual authentication using digital certificates, ensuring that both the user device and the network verify each other’s identity, which is essential for securing wired connections against unauthorized access. On the CompTIA Network+ N10-009 exam, this scenario tests your understanding of how 802.1X integrates with RADIUS and EAP-TLS to meet enterprise authentication requirements; a common trap is choosing MAC filtering or PSK, which lack per-user credential validation. Remember the memory tip: “TLS for TLS” — Transport Layer Security requires certificates on both sides, so EAP-TLS is the only option that uses mutual certificate-based authentication for domain-joined devices.
⚠ Common exam trap
CompTIA often tests the distinction between port security (which is MAC-based and does not authenticate users) and 802.1X (which provides user authentication via RADIUS), leading candidates to mistakenly choose port security when the question explicitly requires domain credential authentication.
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
✓
802.1X with EAP-TLS
802.1X with EAP-TLS is correct because it provides port-based network access control that requires each user to authenticate using their domain credentials (via a RADIUS server) before the switch port is opened for traffic. EAP-TLS uses mutual authentication with digital certificates, ensuring only authorized devices and users gain access to the wired network.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
MAC filtering
Why it's wrong here
MAC filtering only checks the hardware address of the device, not the user. It does not authenticate users with domain credentials and can be bypassed by MAC spoofing.
When this WOULD be correct
A question asking for a simple method to restrict network access to a list of known devices without user authentication, such as in a small office with static devices.
- ✓
802.1X with EAP-TLS
Why this is correct
802.1X with EAP-TLS provides user authentication using certificates, typically tied to domain credentials. It ensures that only authenticated users can gain access to the network, and it can be integrated with Active Directory.
- ✗
WPA2-PSK
Why it's wrong here
WPA2-PSK is a wireless security method that uses a pre-shared key. It is not suitable for wired networks and does not authenticate individual users with domain credentials.
When this WOULD be correct
In a scenario where a small office needs to secure a wireless network for guest access with a simple shared password, and there is no requirement for individual user authentication or integration with domain credentials, WPA2-PSK would be the correct choice.
- ✗
Port security
Why it's wrong here
Port security limits the number of MAC addresses on a switch port or restricts specific MACs, but it does not authenticate users. It can be used as a supplement but not for domain-based user authentication.
When this WOULD be correct
A network administrator needs to prevent unauthorized devices from plugging into switch ports by limiting the number of MAC addresses per port or by allowing only specific MAC addresses. The question would not mention user authentication or domain credentials.
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.
✓802.1X with EAP-TLSCorrect answer▾
Why this is correct
802.1X with EAP-TLS provides user authentication using certificates, typically tied to domain credentials. It ensures that only authenticated users can gain access to the network, and it can be integrated with Active Directory.
✗MAC filteringWrong answer — click to see why▾
Why this is wrong here
MAC filtering only checks device MAC addresses, not user credentials, so it cannot authenticate users with domain credentials.
★ When this WOULD be the correct answer
A question asking for a simple method to restrict network access to a list of known devices without user authentication, such as in a small office with static devices.
Why candidates choose this
Candidates may confuse device-based access control with user authentication, assuming MAC filtering can enforce per-user security.
✗WPA2-PSKWrong answer — click to see why▾
Why this is wrong here
WPA2-PSK is a wireless security protocol, not suitable for wired network authentication. It uses a pre-shared key rather than individual domain credentials, failing to meet the requirement for per-user authentication with domain credentials.
★ When this WOULD be the correct answer
In a scenario where a small office needs to secure a wireless network for guest access with a simple shared password, and there is no requirement for individual user authentication or integration with domain credentials, WPA2-PSK would be the correct choice.
Why candidates choose this
Candidates may confuse wireless security protocols with wired authentication methods, or mistakenly think that WPA2-PSK can be adapted for wired networks, especially if they overlook the 'wired network' specification in the question.
✗Port securityWrong answer — click to see why▾
Why this is wrong here
Port security limits access by MAC address, not by user authentication with domain credentials. It does not require per-user authentication via 802.1X, so it fails to meet the requirement of authenticating each user individually.
★ When this WOULD be the correct answer
A network administrator needs to prevent unauthorized devices from plugging into switch ports by limiting the number of MAC addresses per port or by allowing only specific MAC addresses. The question would not mention user authentication or domain credentials.
Why candidates choose this
Candidates may confuse port security with network access control, thinking it can authenticate users, but it only controls devices based on MAC addresses, not user identity.
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?”
Quick reference
AAA Protocol Comparison
| Protocol | Port(s) | Encryption | Transport | Primary Use |
|---|---|---|---|---|
| RADIUS | 1812 / 1813 | Password only | UDP | Network access control |
| TACACS+ | 49 | Full packet | TCP | Device administration |
| Diameter | 3868 | Full session | TCP / SCTP | Carrier / mobile networks |
| 802.1X | — | EAP-based | Layer 2 | Port-based access control |
TACACS+ encrypts the entire packet; RADIUS only encrypts the password field — a key exam distinction.
Go deeper
Related to this question
Learn chapter
Network Device Hardening
Key term
Switch
A switch is a networking device that connects devices on a local area network and uses MAC addresses to forward data only to the intended recipient.
Key term
Least privilege
Least privilege is a security principle that means giving users, systems, or programs only the minimum permissions they need to do their job and nothing more.
About these practice questions
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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 prevent unauthorized devices from connecting to the network through a switch port. Which security feature should be enabled on the switch?
medium- ✓ A.802.1X
- B.Port security
- C.MAC filtering
- D.Storm control
Why A: 802.1X is the correct answer because it provides port-based network access control (PNAC) that authenticates devices before granting network access. It uses the Extensible Authentication Protocol (EAP) over LAN (EAPoL) to communicate with a RADIUS server, ensuring only authorized users or devices can connect through the switch port. This prevents unauthorized devices from accessing the network at Layer 2, regardless of MAC address or IP configuration.
Variation 2. A network administrator wants to prevent unauthorized devices from connecting to the company's Ethernet ports. The company uses a centralized authentication server. Which IEEE standard should be implemented?
medium- ✓ A.802.1X
- B.802.11i
- C.802.3af
- D.802.1Q
Why A: 802.1X is the IEEE standard for port-based Network Access Control (NAC) that authenticates devices before granting access to an Ethernet port. It uses a centralized authentication server (typically RADIUS) to verify credentials, preventing unauthorized devices from connecting to the network. This directly matches the requirement of controlling access at the port level with a centralized server.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.