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 connecting to the company's Ethernet ports. The company uses a centralized authentication server. Which IEEE standard should be implemented?
IEEE 802.1X provides authentication for devices connecting to a LAN port. It uses EAP exchanges between the supplicant (device), authenticator (switch), and authentication server (RADIUS) to permit or deny access.
B
802.11i
Why wrong: IEEE 802.11i is a wireless security standard that defines WPA2, which provides encryption and authentication for Wi-Fi networks. It is not used for wired Ethernet ports.
C
802.3af
Why wrong: IEEE 802.3af is the Power over Ethernet (PoE) standard, which allows power to be delivered over Ethernet cabling. It does not provide authentication.
D
802.1Q
Why wrong: IEEE 802.1Q is the standard for VLAN tagging, used to identify which VLAN a frame belongs to when traversing a trunk. It does not perform authentication.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
802.1X
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.
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.
✓
802.1X
Why this is correct
IEEE 802.1X provides authentication for devices connecting to a LAN port. It uses EAP exchanges between the supplicant (device), authenticator (switch), and authentication server (RADIUS) to permit or deny access.
Related concept
Read the scenario before looking for a memorised answer.
✗
802.11i
Why it's wrong here
IEEE 802.11i is a wireless security standard that defines WPA2, which provides encryption and authentication for Wi-Fi networks. It is not used for wired Ethernet ports.
✗
802.3af
Why it's wrong here
IEEE 802.3af is the Power over Ethernet (PoE) standard, which allows power to be delivered over Ethernet cabling. It does not provide authentication.
✗
802.1Q
Why it's wrong here
IEEE 802.1Q is the standard for VLAN tagging, used to identify which VLAN a frame belongs to when traversing a trunk. It does not perform authentication.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse 802.1X with wireless security standards like 802.11i, because both involve authentication, but 802.1X is specifically for wired port-based access control.
Detailed technical explanation
How to think about this question
802.1X operates using the Extensible Authentication Protocol (EAP) over LAN (EAPoL) between the supplicant (client) and authenticator (switch), which forwards authentication requests to a RADIUS server. The switch places the port in an unauthorized state until authentication succeeds, and can dynamically assign VLANs or apply ACLs based on the user's identity. In a real-world scenario, a failed authentication might place the port in a guest VLAN with limited access, rather than blocking it entirely.
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 junior network technician can log in to a core router but cannot reach the enable prompt or configuration mode. The AAA server is authenticating the login — but the authorisation policy only grants privilege level 1, not 15. Authentication (who you are) is working; authorisation (what you can do) is not.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this N10-009 question in full detail.
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: 802.1X — 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.
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.
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Question Discussion
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